Systems and Methods for Use of Water with Switchable Ionic Strength

ABSTRACT

Methods and systems for use of switchable water, which is capable of reversibly switching between an initial ionic strength and an increased ionic strength, is described. The disclosed methods and systems can be used, for example, in distillation-free removal of water from solvents, solutes, or solutions, desalination, clay settling, viscosity switching, etc. Switching from lower to higher ionic strength is readily achieved using low energy methods such as bubbling with C0 2 , CS 2  or COS or treatment with Bronsted acids. Switching from higher to lower ionic strength is readily achieved using low energy methods such as bubbling with air, inert gas, heating, agitating, introducing a vacuum or partial vacuum, or any combination or thereof.

FIELD OF THE INVENTION

The field of the invention is solvents, and specifically an aqueoussolvent composition that can be reversibly converted between low ionicstrength and higher ionic strength, and systems and methods of usethereof.

BACKGROUND OF THE INVENTION

Conventional solvents have fixed physical properties which can lead tosignificant limitations in their use as media for reactions andseparations. Many chemical production processes involve multiplereactions and separation steps, and often the type of solvent that isoptimum for any one step is different from that which is optimum for thenext step. Thus it is common for the solvent to be removed after eachstep and a new solvent added in preparation for the next step. Thisremoval and replacement greatly adds to the economic cost andenvironmental impact of the overall process. Therefore, there exists aneed for a solvent that can change its physical properties.

Solvents are commonly used to dissolve material in manufacturing,cleaning, dyeing, extracting, and other processes. In order for asolvent to dissolve a material quickly, selectively, and in sufficientquantity, it is usually necessary for the solvent to have particularphysical properties. Examples of such properties include ionic strength,hydrophobicity, hydrophilicity, dielectric constant, polarizability,acidity, basicity, viscosity, volatility, hydrogen-bond donatingability, hydrogen-bond accepting ability, and polarity. At some point insuch a process after the dissolution, separation of the material fromthe solvent may be desired. Such a separation can be expensive toachieve, especially if the solvent is removed by distillation, whichrequires the use of a volatile solvent, which can lead to significantvapor emission losses and resulting environmental damage, e.g., throughsmog formation. Furthermore, distillation requires a large input ofenergy. It would therefore be desirable to find a non-distillative routefor the removal of solvents from products.

Water is a particularly desirable solvent because of its low price,non-toxicity, nonflammability, and lack of adverse impact on theenvironment, but the separation of water from a product or othermaterial by distillation is particularly expensive in terms of energybecause of the high heat capacity of water and the high heat ofvaporization of water. Therefore the need for a non-distillative routefor the separation of water from products or other materials isparticularly strong.

A common method for separating water from moderately hydrophobic yetwater-soluble materials is “salting out”, a method in which a salt isadded to an aqueous solution that includes a dissolved moderatelyhydrophobic compound, in sufficient amounts to greatly increase theionic strength of the aqueous portion. High ionic strength greatlydecreases the solubility of some compounds in water; thus most of theselected compound or material is forced out of the aqueous phase. Thecompound or material either precipitates (forms a new solid phase),creams out (forms a new liquid phase) or partitions into a pre-existinghydrophobic liquid phase if there is one. This “salting out” methodrequires no distillation but is not preferred because of the expense ofusing very large amounts of salts and, more importantly, because of theexpense of removing the salt from the water afterwards.

SUMMARY OF THE INVENTION

An object of the present invention is to provide systems and methods foruse of water with switchable ionic strength. In an aspect there isprovided a system for switching the ionic strength of water or anaqueous solution, comprising: means for providing an additive comprisingat least one nitrogen atom that is sufficiently basic to be protonatedby carbonic acid; means for adding the additive to water or to anaqueous solution to form an aqueous mixture with switchable ionicstrength; means for exposing the mixture with switchable ionic strengthto an ionizing trigger, such as CO₂, COS, CS₂ or a combination thereof,to raise the ionic strength of the mixture; and means for exposing themixture with raised ionic strength to i) heat, (ii) a flushing gas,(iii) a vacuum or partial vacuum, (iv) agitation, or (v) any combinationthereof, to reform the aqueous mixture with switchable ionic strength.In specific embodiments, this system is used to remove water from ahydrophobic liquid or a solvent or in a desalination process.

In another aspect there is provided a system for controlling the amount,or the presence and absence, of dissolved salt in an aqueous mixturecomprising a compound which reversibly converts to a salt upon contactwith an ionizing trigger in the presence of water, the compound havingthe general formula (1):

where R¹, R², and R³ are independently:

H;

a substituted or unsubstituted C₁ to C₈ aliphatic group that is linear,branched, or cyclic, optionally wherein one or more C of the alkyl groupis replaced by {—Si(R¹⁰)₂—O—} up to and including 8 C being replaced by8 {—Si(R¹⁰)₂—O—};

a substituted or unsubstituted C_(n)Si_(m) group where n and m areindependently a number from 0 to 8 and n+m is a number from 1 to 8;

a substituted or unsubstituted C₄ to C₈ aryl group wherein aryl isoptionally heteroaryl, optionally wherein one or more C is replaced by{—Si(R¹⁰)₂—O—};

a substituted or unsubstituted aryl group having 4 to 8 ring atoms,optionally including one or more {—Si(R¹⁰)₂—O—}, wherein aryl isoptionally heteroaryl;

a —(Si(R¹⁰)₂—O)_(p)— chain in which p is from 1 to 8 which is terminatedby H, or is terminated by a substituted or unsubstituted C₁ to C₈aliphatic and/or aryl group; or

a substituted or unsubstituted (C₁ to C₈ aliphatic)-(C₄ to C₈ aryl)group wherein aryl is optionally heteroaryl, optionally wherein one ormore C is replaced by a {—Si(R¹⁰)₂—O—};

wherein R¹⁰ is a substituted or unsubstituted C₁ to C₈ aliphatic group,a substituted or unsubstituted C₁ to C₈ alkoxy, a substituted orunsubstituted C₄ to C₈ aryl wherein aryl is optionally heteroaryl, asubstituted or unsubstituted aliphatic-alkoxy, a substituted orunsubstituted aliphatic-aryl, or a substituted or unsubstitutedalkoxy-aryl groups; and

wherein a substituent is independently: alkyl; alkenyl; alkynyl; aryl;aryl-halide; heteroaryl; cycloalkyl; Si(alkyl)₃; Si(alkoxy)₃; halo;alkoxyl; amino; alkylamino; alkenylamino; amide; amidine; hydroxyl;thioether; alkylcarbonyl; alkylcarbonyloxy; arylcarbonyloxy;alkoxycarbonyloxy; aryloxycarbonyloxy; carbonate; alkoxycarbonyl;aminocarbonyl; alkylthiocarbonyl; amidine, phosphate; phosphate ester;phosphonato; phosphinato; cyano; acylamino; imino; sulfhydryl;alkylthio; arylthio; thiocarboxylate; dithiocarboxylate; sulfate;sulfato; sulfonate; sulfamoyl; sulfonamide; nitro; nitrile; azido;heterocyclyl; ether; ester; silicon-containing moieties; thioester; or acombination thereof; and a substituent may be further substituted,

wherein when an increase in ionic strength, or the presence of salt, isdesired, the compound is exposed to the ionizing trigger in the presenceof water, resulting in protonation of the compound, and

wherein when a decrease in ionic strength, or the absence of salt, isdesired, any ionizing trigger in said mixture is at a level that isinsufficient to convert the compound to or maintain the compound inprotonated form.

In a further aspect there is provided a system, comprising:

means for providing switchable water which is an aqueous liquid,comprising an additive, that has switchable ionic strength;

means for exposing the switchable water to an ionizing trigger in thepresence of water thereby protonating the additive to form ionicprotonated-additive, which is water-miscible or water-soluble, so thatthe switchable water forms an ionic aqueous liquid;

means for exposing the ionic aqueous liquid to i) heat, (ii) a flushinggas, (iii) a vacuum or partial vacuum, (iv) agitation, or (v) anycombination thereof, thereby expelling the ionizing trigger from theionic aqueous liquid which leads to deprotonation of theprotonated-additive, so that the switchable water forms a non-ionicaqueous liquid; and

optionally, means for separating a selected compound from the ionicaqueous liquid prior to formation of the non-ionic aqueous liquid.

In a further aspect there is provided a system for removing a selectedcompound from a solid material, comprising:

means for contacting a mixture of solid material and selected compoundwith switchable water, which comprises a mixture of water and aswitchable additive in its non-protonated, non-ionic form, so that atleast a portion of the selected compound becomes associated with theswitchable water to form an aqueous non-ionic solution;

optionally, means for separating the solution from residual solidmaterial;

means for contacting the solution with an ionizing trigger in thepresence of water to convert a substantial amount of the switchableadditive from its unprotonated form to its protonated form, resulting ina two-phase liquid mixture having a liquid phase comprising the selectedcompound, and an aqueous ionic liquid phase comprising water and theionic protonated additive; and

means for separating the selected compound from the liquid phase.

Yet another aspect provides a system for modulating an osmotic gradientacross a membrane, comprising:

a semi-permeable membrane;

a switchable water comprising an additive having a switchable ionicstrength on one side of said semi-permeable membrane;

means for contacting the semi-permeable membrane with feed stream; andmeans for contacting the switchable water with an ionizing trigger toionize the additive and thereby increase solute concentration in theswitchable water and modulate the osmotic gradient.

An aspect provides a desalination system comprising:

a semi-permeable membrane that is selectively permeable for water;

a draw solution comprising an additive having switchable ionic strengthand water;

means for introducing an ionizing trigger to the draw solution to ionizethe additive;

means for contacting the semi-permeable membrane with a feed stream ofan aqueous salt solution to permit flow of water from the aqueous saltsolution through the semi-permeable membrane into the draw solutioncomprising the ionized additive; and

means for separating the additive from the water.

Another aspect provides a system for concentrating a dilute aqueoussolution, comprising:

a semi-permeable membrane that is selectively permeable for water;

a draw solution comprising an additive having switchable ionic strength;

means for introducing an ionizing trigger to the draw solution to ionizethe additive;

means for contacting the semi-permeable membrane with a feed stream ofthe dilute aqueous solution to permit flow of water from the diluteaqueous solution through the semi-permeable membrane into the drawsolution comprising the ionized additive; and

optionally, means for separating the additive from the water.

Another aspect provides a method of separating a solute from an aqueoussolution, comprising combining in any order: water; a solute; CO₂, COS,CS₂ or a combination thereof; and an additive that comprises at leastone nitrogen atom that is sufficiently basic to be protonated bycarbonic acid; and allowing separation of two components: a firstcomponent that comprises an ionic form of the additive wherein thenitrogen atom is protonated and water; and a second component thatcomprises the solute; wherein the solute is not reactive with theadditive, CO₂, COS, CS₂ or a combination thereof.

In yet another aspect, there is provided a method for modulating ionicstrength, comprising providing an aqueous solution of lower ionicstrength comprising water and an additive that comprises at least onenitrogen that is sufficiently basic to be protonated by carbonic acid;contacting the aqueous solution of lower ionic strength with CO₂, COS,CS₂ or a combination thereof, to form a higher ionic strength solution;subjecting the higher ionic strength solution to heat, contact with aflushing gas, or heat and contact with a flushing gas; and reforming theaqueous solution of lower ionic strength.

In an aspect, there is provided a method for destabilizing or preventingformation of a dispersion, comprising combining in any order to form amixture: water; a water-immiscible or water-insoluble ingredient; anadditive that comprises at least one nitrogen that is sufficiently basicto be protonated by carbonic acid; and CO₂, COS, CS₂ or a combinationthereof; and allowing the mixture to separate into two components, afirst component comprising the water-immiscible ingredient and a secondcomponent comprising water and an ionic form of the additive.

It should be understood for all aspects and embodiments thereof thatinclude employment of an additive as described in the presentapplication includes employment of more than one additive.

In embodiments of the above aspects, the additive is a compound offormula (1),

where R¹, R², and R³ are each independently:

H;

a substituted or unsubstituted C₁ to C₈ aliphatic group that is linear,branched, or cyclic, optionally wherein one or more C of the alkyl groupis replaced by {—Si(R¹⁰)₂—O—} up to and including 8 C being replaced by8 {—Si(R¹⁰)₂—O—};

a substituted or unsubstituted C_(n)Si_(m) group where n and m areindependently a number from 0 to 8 and n+m is a number from 1 to 8;

a substituted or unsubstituted C₄ to C₈ aryl group wherein aryl isoptionally heteroaryl, optionally wherein one or more C is replaced by a{—Si(R¹⁰)₂—O—};

a —(Si(R¹⁰)₂—O)_(p)— chain in which p is from 1 to 8 which is terminatedby H, or is terminated by a substituted or unsubstituted C₁ to C₈aliphatic and/or aryl group; or

a substituted or unsubstituted (C₁ to C₈ aliphatic)-(C₄ to C₈ aryl)group wherein aryl is optionally heteroaryl, optionally wherein one ormore C is replaced by {—Si(R¹⁰)₂—O—};

wherein R¹⁰ is a substituted or unsubstituted C₁ to C₈ aliphatic group,a substituted or unsubstituted C₁ to C₈ alkoxy, a substituted orunsubstituted C₄ to C₈ aryl wherein aryl is optionally heteroaryl, asubstituted or unsubstituted aliphatic-alkoxy, a substituted orunsubstituted aliphatic-aryl, or a substituted or unsubstitutedalkoxy-aryl group; and wherein a substituent is independently: alkyl;alkenyl; alkynyl; aryl; aryl-halide; heteroaryl; cycloalkyl; Si(alkyl)₃;Si(alkoxy)₃; halo; alkoxyl; amino; alkylamino; dialkylamino,alkenylamino; amide; amidine; hydroxyl; thioether; alkylcarbonyl;alkylcarbonyloxy; arylcarbonyloxy; alkoxycarbonyloxy;aryloxycarbonyloxy; carbonate; alkoxycarbonyl; aminocarbonyl;alkylthiocarbonyl; phosphate; phosphate ester; phosphonato; phosphinato;cyano; acylamino; imino; sulfhydryl; alkylthio; arylthio;thiocarboxylate; dithiocarboxylate; sulfate; sulfato; sulfonate;sulfamoyl; sulfonamide; nitro; nitrile; azido; heterocyclyl; ether;ester; silicon-containing moieties; thioester; or a combination thereof;and a substituent may be further substituted.

In certain embodiments of the above aspects, the ionic form of theadditive is a compound of formula (2)

wherein R¹, R², and R³ are as defined for the compound of formula (1)above, and E is O, S or a mixture of O and S. As would be readilyunderstood by a worker skilled in the art, under appropriate conditionsthe ⁻E₃CH can lose a further hydrogen atom to form ²⁻E₃C and, thereby,protonate a second additive. In a specific embodiment, the ionic form ofprotonated additive comprises a bicarbonate ion. In an alternativeembodiment the ionic form of the additive comprises two protonatedamines and a carbonate ion. Given that the acid-base reaction is anequilibrium reaction, both the carbonate ion and the bicarbonate ion canbe present with the protonated additive ions.

In certain embodiments of the compounds of formulas (1) and (2), one ormore of R¹, R², and R³ comprise one or more nitrogen that issufficiently basic to be protonated by carbonic acid. As would bereadily appreciated by the skilled worker, each of the one or morenitrogen that is sufficiently basic to be protonated by carbonic acid isassociated with a corresponding counter ion E₃CH⁻ in the compound offormula (2).

In certain embodiments of the compounds of formulas (1) and (2), two ofR¹, R², and R³, taken together with the nitrogen to which they areattached, are joined to form a heterocyclic ring. In some embodiments,the heterocyclic ring has 4 to 8 atoms in the ring. In certainembodiments of formula (1) R¹, R², and R³ may be H. R¹, R², and R³ maybe a substituted or unsubstituted C₁ to C₈ alkyl group that is linear,branched, or cyclic, optionally containing 1 to 8 {—Si(R¹⁰)₂—O—}. R¹,R², and R³ may be a substituted or unsubstituted C₂ to C₈ alkenyl groupthat is linear, branched, or cyclic, optionally containing 1 to 8{—Si(R¹⁰)₂—O—}. R¹, R², and R³ may be a substituted or unsubstitutedC_(n)Si_(m) group where n and m are independently a number from 0 to 8and n+m is a number from 1 to 8. R¹, R², and R³ may be a substituted orunsubstituted C₅ to C₈ aryl group optionally containing 1 to 8{—Si(R¹⁰)₂—O—}. R¹, R², and R³ may be a substituted or unsubstitutedheteroaryl group having 4 to 8 atoms in the aromatic ring optionallycontaining 1 to 8 {—Si(R¹⁰)₂—O—}. R¹, R², and R³ may be a—(Si(R¹⁰)₂—O)_(p)— chain in which p is from 1 to 8 which is terminatedby H or a substituted or unsubstituted C₁ to C₈ alkyl group that islinear, branched, or cyclic. R¹, R², and R³ may be a substituted orunsubstituted C₁ to C₈ alkylene-C₅ to C₈ aryl group optionallycontaining 1 to 8 {—Si(R¹⁰)₂—O—}. R¹, R², and R³ may be a substituted orunsubstituted C₂ to C₈ alkenylene-C₅ to C₈ aryl group optionallycontaining 1 to 8 {—Si(R¹⁰)₂—O—}. R¹, R², and R³ may be a substituted orunsubstituted C₁ to C₈ alkylene-heteroaryl group having 4 to 8 atoms inthe aromatic ring optionally containing 1 to 8 {—Si(R¹⁰)₂—O—}. R¹, R²,and R³ may be a substituted or unsubstituted C₂ to C₈alkenylene-heteroaryl group having 4 to 8 atoms in the aromatic ringoptionally containing 1 to 8 {—Si(R¹⁰)₂—O—}. R¹⁰ may be a substituted orunsubstituted: C₁ to C₈ alkyl, C₅ to C₈ aryl, heteroaryl having from 4to 8 carbon atoms in the aromatic ring, or C₁ to C₈ alkoxy moiety.

In embodiments of the above aspects, the additive is a compound offormula (6),

where R¹, R², R³, and R⁴ are independently:

H;

a substituted or unsubstituted C₁ to C₈ aliphatic group that is linear,branched, or cyclic, optionally wherein one or more C of the alkyl groupis replaced by {—Si(R¹⁰)₂—O—} up to and including 8 C being replaced by8 {—Si(R¹⁰)₂—O—};

a substituted or unsubstituted C_(n)Si_(n), group where n and m areindependently a number from 0 to 8 and n+m is a number from 1 to 8;

a substituted or unsubstituted C₄ to C₈ aryl group wherein aryl isoptionally heteroaryl, optionally wherein one or more C is replaced by{—Si(R¹⁰)₂—O—};

a substituted or unsubstituted aryl group having 4 to 8 ring atoms,optionally including one or more {—Si(R¹⁰)₂—O—}, wherein aryl isoptionally heteroaryl;

a —(Si(R¹⁰)₂—O)_(p)— chain in which p is from 1 to 8 which is terminatedby H, or is terminated by a substituted or unsubstituted C₁ to C₈aliphatic and/or aryl group; or

a substituted or unsubstituted (C₁ to C₈ aliphatic)-(C₄ to C₈ aryl)group wherein aryl is optionally heteroaryl, optionally wherein one ormore C is replaced by a {—Si(R¹⁰)₂—O—};

wherein R¹⁰ is a substituted or unsubstituted C₁ to C₈ aliphatic group,a substituted or unsubstituted C₁ to C₈ alkoxy, a substituted orunsubstituted C₄ to C₈ aryl wherein aryl is optionally heteroaryl, asubstituted or unsubstituted aliphatic-alkoxy, a substituted orunsubstituted aliphatic-aryl, or a substituted or unsubstitutedalkoxy-aryl groups; and

wherein a substituent is independently: alkyl; alkenyl; alkynyl; aryl;aryl-halide; heteroaryl; cycloalkyl; Si(alkyl)₃; Si(alkoxy)₃; halo;alkoxyl; amino; alkylamino; alkenylamino; amide; amidine; hydroxyl;thioether; alkylcarbonyl; alkylcarbonyloxy; arylcarbonyloxy;alkoxycarbonyloxy; aryloxycarbonyloxy; carbonate; alkoxycarbonyl;aminocarbonyl; alkylthiocarbonyl; amidine, phosphate; phosphate ester;phosphonato; phosphinato; cyano; acylamino; imino; sulfhydryl;alkylthio; arylthio; thiocarboxylate; dithiocarboxylate; sulfate;sulfato; sulfonate; sulfamoyl; sulfonamide; nitro; nitrile; azido;heterocyclyl; ether; ester; silicon-containing moieties; thioester; or acombination thereof; and a substituent may be further substituted.

In certain embodiments of the above aspects, the ionic form of theadditive is a compound of formula (6′):

wherein R¹, R², R³ and R⁴ are as defined for the compound of formula (6)above, and E is O, S or a mixture of O and S.

In embodiments of the above aspects, the at least one nitrogen beingsufficiently basic to be protonated by carbonic acid is the at least onenitrogen having a conjugate acid with a pK_(a) range from about 6 toabout 14, or about 8 to about 10.

In certain embodiments of the above aspects, the additive is MDEA(N-methyl diethanol-amine); TMDAB (N,N, N′,N′-tetramethyl-1,4-diaminobutane); THEED(N,N,N′,N′-tetrakis(2-hydroxyethyl)ethylenediamine); DMAPAP(1-[bis[3-(dimethylamino)]propyl]amino]-2-propanol); HMTETA(1,1,4,7,10,10-hexamethyl triethylenetetramine) or DIAC(N′,N″-(butane-1,4-diyl)bis(N,N-dimethylacetimidamide.

In an embodiment of certain aspects, the dilute aqueous solution iswastewater.

In certain embodiments of the aspect of a method for destabilizing orpreventing formation of a dispersion, the combining in any ordercomprises forming a mixture by adding the additive to an aqueoussolution that comprises the solute; and contacting the mixture with CO₂,COS, CS₂ or a combination thereof. In another embodiment, the combiningin any order comprises forming a mixture by adding the solute to wateror an aqueous solution; contacting the mixture with CO₂, COS, CS₂ or acombination thereof; and adding the additive. In yet another embodiment,the combining in any order comprises forming a mixture by adding thesolute to an aqueous solution that comprises the additive; andcontacting the mixture with CO₂, COS, CS₂ or a combination thereof. Inanother embodiment, the combining in any order comprises adding amixture comprising the solute and the additive to an aqueous solutionthat comprises CO₂, COS, CS₂ or a combination thereof. In anotherembodiment, the combining in any order comprises forming a mixture byadding the solute to an aqueous solution that comprises CO₂, COS, CS₂ ora combination thereof, and adding the additive.

In certain embodiments of this aspect, the solute comprises a product ofa chemical reaction. The first component may further comprise awater-soluble catalyst. The solute may comprise a catalyst. In anotherembodiment of certain aspects, combining further comprises combining thewater, the solute, the additive, and the CO₂, COS, CS₂ or a combinationthereof, with a hydrophobic liquid, wherein after the separating stepthe second component comprises the hydrophobic liquid.

In certain embodiments, a mixture of water, the solute, and the additiveis a homogeneous liquid. In other embodiments, a mixture of water andthe ionic form of the additive is a homogeneous liquid. In yet anotherembodiment, a mixture of water and the ionic form of the additive is asuspension. In another embodiment, a mixture of water and the ionic formof the additive is a solid. In certain embodiments the solute is solubleor miscible in low ionic strength aqueous solutions and is insoluble orimmiscible in high ionic strength aqueous solutions.

Some embodiments further comprise isolating the first component, andsubjecting it to a trigger to form an aqueous solution comprising theadditive, wherein the trigger is heat, bubbling with a flushing gas, orheat and bubbling with a flushing gas. In certain embodiments, isolatingincludes centrifuging, decanting, filtering, or a combination thereof.In certain embodiments, the additive is water-soluble or water-misciblein both its ionized form and its non-ionized form. In certainembodiments, only the ionized form of the additive is water-soluble orwater-miscible and the non-ionized form is water insoluble orimmiscible.

In certain embodiments of the above aspects, number of moles of water inthe aqueous solution and number of moles of basic nitrogen in theadditive in the aqueous solution is approximately equivalent. In otherembodiments of the above aspects, number of moles of water in theaqueous solution is in excess over number of moles of basic nitrogen inthe additive in the aqueous solution.

In an embodiment of the aspect regarding a method for destabilizing orpreventing formation of a dispersion, the dispersion is an emulsion andthe water-immiscible ingredient is a liquid or a supercritical fluid. Inother embodiments, the dispersion is a reverse emulsion and thewater-immiscible ingredient is a liquid or a supercritical fluid. In yetanother embodiment of this aspect, the dispersion is a foam and thewater-immiscible ingredient is a gas. In other embodiments of thisaspect, the dispersion is a suspension and the water-immiscibleingredient is a solid. In embodiments of the aspects described herein, amixture may further comprise a surfactant.

In an embodiment of the aspect regarding the method for modulating ionicstrength, the method is used as a sensor of CO₂, COS or CS₂; a detectorof CO₂, COS or CS₂; a chemical switch; a surfactant deactivator; or toconduct electricity.

In further embodiments of the aspect regarding a method of separating asolute from an aqueous solution, the aspect regarding modulating ionicstrength, and the aspect regarding a method for destabilizing orpreventing formation of a dispersion are used to remove water from ahydrophobic liquid or a solvent.

In further embodiments, methods of these aspects are used in adesalination process or a wastewater treatment process.

Another aspect provides a system having a modulatable osmotic gradientacross a membrane, comprising:

a semi-permeable membrane;

a switchable water located on one side of said semi-permeable membrane,said switchable water comprising water and an additive switchablebetween a first form and a second form, wherein said second form of theadditive includes at least one ionized functional group that is neutralin said first form of the additive, such that switching the additivefrom the first form to the second form increases the osmotic pressure ofthe switchable water;

means for contacting the semi-permeable membrane with a feed stream onthe other side of said permeable membrane; and

means for contacting the switchable water with an ionizing trigger toionize at least one functional group in the additive and therebyincrease the ionic strength of the switchable water and modulate theosmotic gradient across the membrane.

Another aspect provides a system for destabilization of a suspension,comprising:

a mixture of water or an aqueous solution and one or more particlesolids that are substantially insoluble in water;

a switchable water comprising water and an additive switchable between afirst form and a second form, wherein said second form of the additiveincludes at least one ionized functional group that is neutral in saidfirst form of the additive, such that switching the additive from thefirst form to the second form increases the ionic strength of theswitchable water; and

means for contacting the switchable water with an ionizing trigger toionize at least one functional group in the additive and therebyincrease the ionic strength of the switchable water to stop theformation of a suspension of the one or more particle solids ordestabilize a suspension of the one or more fine particle solids.

Another aspect provides a method for destabilizing a suspension orpreventing formation of a suspension, comprising:

combining, in any order, to form a mixture:

-   -   water or an aqueous solution and one or more particle solids        that are substantially insoluble in water;    -   an additive switchable between a first form and a second form,        wherein said second form of the additive includes at least one        ionized functional group that is neutral in said first form of        the additive; and        -   an ionizing trigger to ionize the at least one functional            group in the additive and thereby increase the ionic            strength of the mixture to stop the formation of a            suspension of the one or more particle solids or destabilize            a suspension of the one or more particle solids; and

allowing the mixture to separate into two components, a first componentcomprising the particle solids and a second component comprising waterand an ionic form of the additive.

Another aspect provides a method for removing a solute from an aqueoussolution or concentrating a dilute aqueous solution, comprising thesteps of:

providing a semi-permeable membrane that is selectively permeable forwater and has on one side a draw solution that is a switchable watercomprising water and an additive switchable between a first form and asecond form, wherein said second form of the additive includes at leastone ionized functional group that is neutral in said first form of theadditive;

contacting the draw solution with an ionizing trigger to switch theadditive to the second form before or after association with thesemi-permeable membrane, thereby increasing the osmotic pressure of thedraw solution;

contacting the semi-permeable membrane with a feed stream of the aqueoussolution to permit water to flow from the aqueous solution through thesemi-permeable membrane into the increased ionic strength draw solution;and

optionally, removing the additive from the resulting diluted drawsolution.

Another aspect provides a system and method for modulating viscosity ofan aqueous solution or mixture. The system for modulating viscosity ofwater or an aqueous solution, comprises:

water or an aqueous solution having a first viscosity in combinationwith an additive switchable between a first form and a second form,wherein said second form of the additive includes at least one ionizedfunctional group that is neutral in said first form of the additive,such that switching the additive from the first form to the second formincreases the ionic strength of the switchable water; and

means for contacting the combination with an ionizing trigger to ionizeat least one functional group in the additive and thereby increase theionic strength of the switchable water and change the viscosity of thecombination to a second viscosity.

The method for modulating viscosity comprises:

adding to the water or aqueous solution an additive that is switchablebetween a first form and a second form to produce a mixture, whereinsaid second form of the additive includes at least one ionizedfunctional group that is neutral in said first form of the additive,such that switching the additive from the first form to the second formincreases the ionic strength of the switchable water; and

contacting the mixture formed in step (a) with an ionizing trigger toionize at least one functional group in the additive and therebyincrease the ionic strength of the switchable water and change theviscosity of the mixture to a second viscosity.

Another aspect provides a system for homogeneous catalysis, comprising:

a hydrophilic catalyst;

an organic solvent;

a switchable water comprising water and an additive switchable between afirst form and a second form, wherein said second form of the additiveincludes at least one ionized functional group that is neutral in saidfirst form of the additive, such that switching the additive from thefirst form to the second form increases the ionic strength of theswitchable water; and

means for contacting the switchable water with an ionizing trigger toionize at least one functional group in the additive and therebyincrease the ionic strength of the switchable water,

wherein the organic solvent is miscible with the switchable water whenthe additive is in the first form and immiscible or poorly miscible withthe switchable water when the ionic strength is increased by switchingthe additive to the second form.

Another aspect provides a method for homogeneous catalysis, comprising:

forming a homogeneous reaction mixture by combining, in any order: ahydrophilic catalyst; one or more reactants; an organic solvent; wateror an aqueous solution; and an additive in a first form, wherein theadditive is switchable from the first form to a second form thatincludes at least one ionized functional group that is neutral in saidfirst form of the additive;

allowing the reactants to react to form one or more products; and

subsequently contacting the homogeneous mixture with an ionizing triggerto switch the additive to its second form, by ionizing at least onefunctional group in the additive, and increase the ionic strength of themixture to salt out the organic solvent and the one or more products,

wherein the organic solvent is miscible with water when the additive isin the first form and immiscible or poorly miscible with water when theionic strength is increased by switching the additive to the secondform.

Another aspect provides a system for modulating ionic strength of anaqueous solution comprising:

a switchable water comprising water and an additive switchable between afirst form and a second form, wherein said second form of the additiveincludes at least one ionized functional group that is neutral in saidfirst form of the additive, such that switching the additive from thefirst form to the second form increases the ionic strength of theswitchable water; and

means for contacting the switchable water with an ionizing trigger toionize at least one functional group in the additive and therebyincrease the ionic strength of the switchable water,

wherein the additive is a polymer.

Another aspect provides a method for modulating the ionic strength of anaqueous solution, comprising:

contacting a switchable water comprising water and an additiveswitchable between a first form and a second form, wherein said secondform of the additive includes at least one ionized functional group thatis neutral in said first form of the additive, such that switching theadditive from the first form to the second form increases the ionicstrength of the switchable water with an ionizing trigger to ionize atleast one functional group in the additive and thereby increase theionic strength of the switchable water,

wherein the additive is a polymer.

In accordance with certain embodiments of all the above aspects, theswitchable water additive is a monoamine, a diamine, a triamine, atetraamine or a polyamine, such as a polymer or a biopolymer.

In accordance with another aspect there is provided a polymer that is:

a functionalized branched or linear polyethyleneimine, such as amethylated polyethyleneimine (“MPEI”), an ethylated polyethyleneimine(“EPEI”), a propylated polyethyleneimine (“PPEI”), or a butylatedpolyethyleneimine (“BPEI”);

a functionalized polymethyl methacrylate (“PMMA”) based polymer, such as3-(dimethylamino)-1-propylamine functionalized PMMA;

a functionalized polyacrylic acid (“FAA”) polymer, such as,3-(dimethylannino)-1-propylamine functionalized FAA;

an amine-containing polyacrylic acid salt;

a functionalized poly(methyl methacrylate-co-styrene) (“PMMA/PS”), suchas a 3-(dimethylamino)-1-propylamine functionalized PMMA/PS; or

a polymer synthesized form amine-containing monomers, such as apolydiethylaminoethylmethacrylate (“PDEAEMA”).

BRIEF DESCRIPTION OF THE DRAWINGS

Embodiments of the invention will now be described, by way of example,with reference to the accompanying drawings.

FIG. 1 shows a chemical reaction equation and a schematic of theswitching reaction between differing ionic strength forms of an aqueoussolution of an amine.

FIG. 2 presents the chemical structures of various tertiary aminesuseful as additives in the present invention.

FIG. 3 shows multiple ¹H NMR spectra from switchability study of MDEAcarried out in D₂O at 400 MHz. Spectrum A was captured with no CO₂treatment, spectrum B was captured after 20 minutes of CO₂ bubbling, andspectrum C was captured after 300 minutes of N₂ bubbling. This isdiscussed in Example 4 below.

FIG. 4 shows multiple ¹H NMR spectra from a switchability study of DMAEcarried out in D₂O at 400 MHz. Spectrum A was captured with no CO₂treatment, spectrum B was captured after 30 minutes of CO₂ bubbling, andspectrum C was captured after 240 minutes of N₂ bubbling. This isdiscussed in Example 4 below.

FIG. 5 shows multiple ¹H NMR spectra from a switchability study ofHMTETA carried out in D₂O at 400 MHz. Spectrum A was captured with noCO₂ treatment, spectrum B was captured after 20 minutes of CO₂ bubbling,and spectrum C was captured after 240 minutes of N₂ bubbling. This isdiscussed in Example 4 below.

FIG. 6 shows multiple ¹H NMR spectra from a switchability study ofDMAPAP carried out in D₂O at 400 MHz. Spectrum A was captured with noCO₂ treatment, spectrum B was captured after 20 minutes of CO₂ bubbling,and spectrum C was captured after 120 minutes of N₂ bubbling. This isdiscussed in Example 4 below.

FIG. 7 shows conductivity spectra for the responses of water and 1:1 v/vH₂O: DMAE; 1:1 v/v H₂O: MDEA; and 1:1 w/w H₂O: THEED solutions to a CO₂trigger over time. This is discussed in Example 5 below.

FIG. 8 shows conductivity spectra for the responses of 1:1 v/v H₂O:DMAE; 1:1 v/v H₂O: MDEA; and 1:1 w/w H₂O: THEED solutions, which hadbeen switched with a CO₂ trigger, to the removal of CO₂ by nitrogenbubbling over time. This is discussed in Example 5 below.

FIG. 9 shows a plot of the degree of protonation of 0.5 M solutions ofDMAE and MDEA in D₂O and a 0.1 M aqueous solution of THEED in D₂Oresulting from exposure to a CO₂ trigger over time. This is discussed inExample 6 below.

FIG. 10 shows a plot of the degree of deprotonation of 0.5 M solutionsof DMAE and MDEA in D₂O and a 0.1 M solution of THEED in D₂O which havebeen switched with a CO₂ trigger to the removal of the trigger bynitrogen bubbling over time. This is discussed in Example 6 below.

FIG. 11 shows conductivity spectra for the responses of 1:1 v/v H₂O:amine solutions to a CO₂ trigger over time, in which the amine is TMDAB(♦), HMTETA (▪), and DMAPAP (▴). This is discussed in Example 7 below.

FIG. 12 shows conductivity spectra for the responses of 1:1 v/v H₂O:amine solutions, which have been switched with a CO₂ trigger, to theremoval of the trigger by nitrogen bubbling over time, in which theamine is TMDAB (♦), HMTETA (▪), and DMAPAP (▴). This is discussed inExample 7 below.

FIG. 13 shows five photographs A-E representing different stages of anexperiment exhibiting how the switchable ionic strength character ofamine additive TMDAB can be used to disrupt an emulsion of water andn-decanol. This is discussed in Example 8 below.

FIG. 14A-C schematically depict studies performed to monitor claysettling in switchable water according to various embodiments (FIG. 14A;Study 1 of Example 12; FIG. 14B Study 2 of Example 12; and FIG. 14CStudy 3 of Example 12).

FIG. 15A-D shows the results of mixing a switchable water with kaoliniteclay fines and treatment with CO₂ followed by treatment with N₂ (FIG.15A clay+1 mM TMDAB; FIG. 15B clay+1 mM TMDAB after 1 hour CO₂; FIG. 15Cclay+1 mM TMDAB-CO₂ by addition of N₂ for 1 h; and FIG. 15D photographsof mixtures+TMDAB, after CO₂, and after N₂).

FIG. 16A-B shows the results of mixing a switchable water with kaoliniteclay fines and treatment with CO₂ in the presence of clay (FIG. 16Aclay+1 mM TMDAB after 1 hour CO₂; and FIG. 16D photographs ofmixtures+TMDAB after CO₂, and after N₂).

FIG. 17A-C shows the results of mixing a CO₂ treated filtrate (obtainedfrom a mixture of switchable water with kaolinite clay fines) with clay(FIG. 17A 1 h CO₂ filtrate+clay; FIG. 17B CO₂ blank+clay (control); FIG.17C photographs of mixtures CO₂ filtrate+clay and CO₂ blank+clay(control)).

FIG. 18 depicts a standard system for seawater desalination usingforward osmosis.

FIG. 19 depicts a system and process for desalination by forward osmosisfollowed by reverse osmosis using a switchable water (“SW on” refers tothe bicarbonate form of the switchable water and “SW off” refers to thenon-ionized form of the switchable water).

FIG. 20 depicts an alternative system and process for desalination byforward osmosis followed by removal of CO₂ (by heat or bubbling of anon-acidic gas) causing separation of much or all of the additive fromthe water, using a switchable water (“SW on” refers to the bicarbonateform of the switchable water and “SW off” refers to the non-ionized formof the switchable water). In such a process, if the separation of theswitchable water additive from the water is incomplete, reverse osmosisor nanofiltration can be used to remove the remaining additive from thewater.

FIG. 21 depicts a system that includes means for reversibly converting anon-ionized form of switchable water to an ionized form of theswitchable water.

FIG. 22 depicts a system for obtaining at least one compound from amixture of compounds using switchable water that is reversibly switchedfrom its non-ionic form to an ionized form.

FIG. 23A shows the results of mixing a switchable water, comprising aBPEI, MW 600, switchable additive at low concentration, withmontmorillonite in the absence of CO₂.

FIG. 23B shows the results of mixing a switchable water, comprising aBPEI, MW 600, switchable additive at low concentration, withmontmorillonite in the presence of CO₂.

FIG. 24 shows a photograph of the results of mixing switchable water,comprising a EPEI, MW 600, switchable additive at low concentration,with montmorillonite in the absence (left) and presence (right) of CO₂.

FIG. 25 shows the results of mixing a switchable water, comprising anamine functionalized PMMA, MW 120 K, switchable additive at lowconcentration, with montmorillonite in the presence of CO₂.

FIG. 26A shows the results of mixing a switchable water, comprising3-(dimethylamino)-1-propylamine functionalized PMMA/PS (10 mol %styrene, MW=10,600-15,900) switchable additive at low concentration,with montmorillonite in the absence of CO₂.

FIG. 26B shows the results of mixing a switchable water, comprising3-(dimethylamino)-1-propylamine functionalized PMMA/PS (10 mol %styrene, MW=10,600-15,900) switchable additive at low concentration,with montmorillonite in the presence of CO₂.

FIG. 27 shows a photograph of the results of mixing switchable water,comprising 3-(dimethylamino)-1-propylamine functionalized PMMA(MW=120,000) switchable additive at low concentration, with kaolinite inthe absence (left) and presence (right) of CO₂.

FIG. 28A shows the results of mixing water and polyacrylamide, 6000 K,with montmorillonite in the absence of CO₂.

FIG. 28B shows esults of mixing water and polyacrylamide, 6000 K, withmontmorillonite in the presence of CO₂.

FIG. 29 depicts a schematic of a method and system using switchablewater in process for the hydroformylation of styrene.

FIG. 30 shows the results of hydroformylation of styrene using DMEA as aswitchable water additive. (Left) All reagents mixed before reaction orCO₂ treatment. (Centre) After completion of the hydroformylationreaction. (Right) After CO₂ treatment for 45 minutes. From Top toBottom: Cycles 1 to 3 using the same catalyst and aqueous phase.

FIG. 31 shows the settling profile of CO₂-treated kaolinite suspensionin a blank, 1 mM, 10 mM, and 100 mM TMDAB solutions.

FIG. 32 graphically shows the results of mixing a switchable water,comprising a TMDAB, switchable additive, with kaolinite in the presenceof CO₂.

FIG. 33 is a photograph showing the results of mixing a switchablewater, comprising a TMDAB, switchable additive, with kaolinite in thepresence of CO₂.

FIG. 34 shows supernatant from kaolinite settling experiment after 2hours. From left to right: no treatment, CO₂ blank, 0.01 mM, 0.1 mM, 1mM, 10 mM, and 100 mM TMDAB. All suspensions with TMDAB were subjectedto CO₂ treatment.

FIG. 35 shows the zeta potentials of kaolinite clay particles underdifferent treatment conditions.

FIG. 36 shows the particle size of kaolinite clay under differenttreatment conditions.

FIG. 37 shows the settling profile of CO₂-treated kaolinite suspensionwith different clay loadings.

FIG. 38 shows the effect of kaolinite clay loading on the turbidity ofthe supernatant water after settling in the presence of either CO₂ orboth 1 mM TMDAB and CO₂.

FIG. 39 shows settling profiles of a kaolinite suspension treated with 1mM TMDAB and CO₂ and two different controls (pH and ionic strengthadjusted).

FIG. 40 shows settling profiles of a kaolinite suspension treated with10 mM TMDAB and CO₂ and two different controls (pH and ionic strengthadjusted).

FIG. 41 depicts turbidity measurements of kaolinite settling experimentswith different concentrations of TMDAB and three controls (pH and ionicstrength adjusted) and CO₂ blank.

FIG. 42 depicts zeta potentials of kaolinite settling experiments withdifferent concentrations of TMDAB and three controls (pH and ionicstrength adjusted) and CO₂ blank.

FIG. 43 shows chemical force titration curve showing the tip-sampleadhesive force as a function of pH between an Au-coated AFM tipterminated with a SAM of 12-phenyldodecylthiol or 12-mercaptododecanoicacid and (a) silica substrate or (b) mica substrate. The forces measuredbetween the silica substrate and the acid tip are scaled by a factor of10 relative to other three sets of data. The error bars represent the95% confidence interval in the adhesion force as measured from anaverage of at least 1000 force-distance curves.

FIG. 44 shows a schematic of a switchable surfactant (C8) in neutralform (left) and surfactant form (right).

FIG. 45 shows a schematic of a switchable amidine (C4) in the absence ofCO₂ (left) and in the presence of CO₂ (right).

DETAILED DESCRIPTION OF THE INVENTION Definitions

Unless defined otherwise, all technical and scientific terms used hereinhave the same meaning as commonly understood by one of ordinary skill inthe art to which this invention belongs.

As used in the specification and claims, the singular forms “a”, “an”and “the” include plural references unless the context clearly dictatesotherwise.

The term “comprising” as used herein will be understood to mean that thelist following is non-exhaustive and may or may not include any otheradditional suitable items, for example one or more further feature(s),component(s) and/or ingredient(s) as appropriate.

As used herein, “aliphatic” refers to hydrocarbon moieties that arelinear, branched or cyclic, may be alkyl, alkenyl or alkynyl, and may besubstituted or unsubstituted. “Alkenyl” means a hydrocarbon moiety thatis linear, branched or cyclic and contains at least one carbon to carbondouble bond. “Alkynyl” means a hydrocarbon moiety that is linear,branched or cyclic and contains at least one carbon to carbon triplebond. “Aryl” means a moiety including a substituted or unsubstitutedaromatic ring, including heteroaryl moieties and moieties with more thanone conjugated aromatic ring; optionally it may also include one or morenon-aromatic ring. “C₅ to C₈ Aryl” means a moiety including asubstituted or unsubstituted aromatic ring having from 5 to 8 carbonatoms in one or more conjugated aromatic rings. Examples of arylmoieties include phenyl.

“Heteroaryl” means a moiety including a substituted or unsubstitutedaromatic ring having from 4 to 8 carbon atoms and at least oneheteroatom in one or more conjugated aromatic rings. As used herein,“heteroatom” refers to non-carbon and non-hydrogen atoms, such as, forexample, O, S, and N. Examples of heteroaryl moieties include pyridyltetrahydrofuranyl and thienyl.

“Alkylene” means a divalent alkyl radical, e.g., —C_(f)H_(2f)— wherein fis an integer. “Alkenylene” means a divalent alkenyl radical, e.g.,—CHCH—. “Alkynylene” means a divalent alkynyl radical. “Arylene” means adivalent aryl radical, e.g., —C₆H₄—. “Heteroarylene” means a divalentheteroaryl radical, e.g., —O₅H₃N—. “Alkylene-aryl” means a divalentalkylene radical attached at one of its two free valencies to an arylradical, e.g., —CH₂—C₆H₅. “Alkenylene-aryl” means a divalent alkenyleneradical attached at one of its two free valencies to an aryl radical,e.g., —CHCH—C₆H₅. “Alkylene-heteroaryl” means a divalent alkyleneradical attached at one of its two free valencies to a heteroarylradical, e.g., —CH₂—C₅H₄N. “Alkenylene-heteroaryl” means a divalentalkenylene radical attached at one of its two free valencies to aheteroaryl radical, e.g., —CHCH—C₅H₄N—.

“Alkylene-arylene” means a divalent alkylene radical attached at one ofits two free valencies to one of the two free valencies of a divalentarylene radical, e.g., —CH₂—C₆H₄—. “Alkenylene-arylene” means a divalentalkenylene radical attached at one of its two free valencies to one ofthe two free valencies of a divalent arylene radical, e.g., —CHCH—C₆H₄—.“Alkynylene-arylene” means a divalent alkynylene radical attached at oneof its two free valencies to one of the two free valencies of a divalentarylene radical, e.g., —C≡C—C₆H₄—.

“Alkylene-heteroarylene” means a divalent alkylene radical attached atone of its two free valencies to one of the two free valencies of adivalent heteroarylene radical, e.g., —CH₂—C₅H₃N—.“Alkenylene-heteroarylene” means a divalent alkenylene radical attachedat one of its two free valencies to one of the two free valencies of adivalent heterarylene radical, e.g., —CHCH—C₅H₃N—.“Alkynylene-heteroarylene” means a divalent alkynylene radical attachedat one of its two free valencies to one of the two free valencies of adivalent arylene radical, e.g., —C≡C—C₅H₃N—.

“Substituted” means having one or more substituent moieties whosepresence does not interfere with the desired reaction. Examples ofsubstituents include alkyl, alkenyl, alkynyl, aryl, aryl-halide,heteroaryl, cycloalkyl (non-aromatic ring), Si(alkyl)₃, Si(alkoxy)₃,halo, alkoxyl, amino, alkylamino, alkenylamino, amide, amidine,hydroxyl, thioether, alkylcarbonyl, alkylcarbonyloxy, arylcarbonyloxy,alkoxycarbonyloxy, aryloxycarbonyloxy, carbonate, alkoxycarbonyl,aminocarbonyl, alkylthiocarbonyl, phosphate, phosphate ester,phosphonato, phosphinato, cyano, acylamino, imino, sulfhydryl,alkylthio, arylthio, thiocarboxylate, dithiocarboxylate, sulfate,sulfato, sulfonate, sulfamoyl, sulfonamide, nitro, nitrile, azido,heterocyclyl, ether, ester, silicon-containing moieties, thioester, or acombination thereof. Preferable substituents are alkyl, aryl,heteroaryl, and ether. It is noted that aryl halides are acceptablesubstituents. Alkyl halides are known to be quite reactive, and areacceptable so long as they do not interfere with the desired reaction.The substituents may themselves be substituted. For instance, an aminosubstituent may itself be mono or independently disubstituted by furthersubstituents defined above, such as alkyl, alkenyl, alkynyl, aryl,aryl-halide and heteroaryl cycloalkyl (non-aromatic ring).

“Short chain aliphatic” or “lower aliphatic” refers to C₁ to O₄aliphatic. “Long chain aliphatic” or “higher aliphatic” refers to C₅ toC₈ aliphatic.

As used herein, the term “unsubstituted” refers to any open valence ofan atom being occupied by hydrogen. Also, if an occupant of an openvalence position on an atom is not specified then it is hydrogen.

As used herein, the term “polymer” means a molecule of high relativemolecular mass, the structure of which essentially comprises multiplerepetition of units derived from molecules of low relative molecularmass. Included within the term “polymer” are biopolymers. The term“bio-polymer,” as used herein, refers to a naturally occurring polymer.Naturally occurring polymers include, but are not limited to, proteinsand carbohydrates. The term “bio-polymer” also includes derivatisedforms of the naturally occurring polymers that have been modified toinclude one or more pendant amines. As used herein, the term “oligomer”means a molecule of intermediate relative molecular mass, the structureof which essentially comprises a small plurality of units derived frommolecules of low relative molecular mass. A molecule can be regarded ashaving a high relative molecular mass if the addition or removal of oneor a few of the units has a negligible effect on the molecularproperties. A molecule can be regarded as having an intermediaterelative molecular mass if it has molecular properties which do varysignificantly with the removal of one or a few of the units. (See IUPACRecommendations 1996 in (1996) Pure and Applied Chemistry 68:2287-2311.)

The term “switched” means that the physical properties and in particularthe ionic strength, have been modified. “Switchable” means able to beconverted from a first state with a first set of physical properties,e.g., a first state of a given ionic strength, to a second state with asecond set of physical properties, e.g., a state of higher ionicstrength. A “trigger” is a change of conditions (e.g., introduction orremoval of a gas, change in temperature) that causes a change in thephysical properties, e.g., ionic strength. The term “reversible” meansthat the reaction can proceed in either direction (backward or forward)depending on the reaction conditions.

“Carbonated water” means a solution of water in which CO₂ has beendissolved. “CO₂ saturated water” means a solution of water in which CO₂is dissolved to the maximum extent at that temperature.

As used herein, “a gas that has substantially no carbon dioxide” meansthat the gas has insufficient CO₂ content to interfere with the removalof CO₂ from the solution. For some applications, air may be a gas thathas substantially no CO₂. Untreated air may be successfully employed,i.e., air in which the CO₂ content is unaltered; this would provide acost saving. For instance, air may be a gas that has substantially noCO₂ because in some circumstances, the approximately 0.04% by volume ofCO₂ present in air is insufficient to maintain a compound in a switchedform, such that air can be a trigger used to remove CO₂ from a solutionand cause switching. Similarly, “a gas that has substantially no CO₂,CS₂ or COS” has insufficient CO₂, CS₂ or COS content to interfere withthe removal of CO₂, CS₂ or COS from the solution.

As used herein, “additive” refers to a compound comprising at least oneamine or amidine nitrogen that is sufficiently basic that when it is inthe presence of water and CO₂ (which form carbonic acid), for example,the amine or amidine nitrogen becomes protonated. When an aqueoussolution that includes such a switchable additive is subjected to atrigger, the additive reversibly switches between two states, anon-ionized state where the nitrogen is trivalent and is uncharged, andan ionized state where the nitrogen is protonated making it a positivelycharged nitrogen atom. In some cases such as protonated amidines, thepositive charge may be delocalized over more than one atom. Forconvenience herein, the uncharged or non-ionic form of the additive isgenerally not specified, whereas the ionic form is generally specified.The terms “ionized” or “ionic” as used herein in identifying a form theadditive merely refer to the protonated or charged state of the amine oramidine nitrogen. For example, in certain examples, the additiveincludes other functional groups that are ionized when the amine oramidine nitrogen(s) is in the uncharged or non-ionic form.

As would be readily appreciated by a worker skilled in the art, sincefew protonation reactions proceed to completion, when a compound isreferred to herein as being “protonated” it means that all, or only themajority, of the molecules of the compound are protonated. For example,when the additive has a single N atom, more than about 90%, or more thanabout 95%, or about 95%, of the molecules are protonated by carbonicacid.

As used herein, “amine additive” (see compound of formula (1) below)refers to a molecule with a structure R¹R²R³N, where R¹ through R³ areindependently hydrogen or aliphatic or aryl, which includes heteroaryl,as discussed below. The ionic form of an amine (see compound of formula(2) below) is termed an “ammonium salt”. The bicarbonate salt of anamine (see compound of formula (3) below) is termed an “ammoniumbicarbonate”.

As used herein, “amidine additive” refers to a molecule with a structureR¹N═C(R²)—NR³R⁴, where R¹ through R⁴ are independently hydrogen oraliphatic or aryl, which includes heteroaryl, or siloxyl, as discussedbelow. The ionic form of an amidine (see compound of formula (6′) below)is termed an “amidinium salt”.

As used herein, the term “a basic nitrogen” or “a nitrogen that issufficiently basic to be protonated by carbonic acid” is used to denotea nitrogen atom that has a lone pair of electrons available andsusceptible to protonation. Although carbonic acid (CO₂ in water) ismentioned, such a nitrogen would also be protonated by CS₂ in water andCOS in water. This term is intended to denote the nitrogen's basicityand it is not meant to imply which of the three trigger gases (CO₂, CS₂or COS) is used.

“Ionic” means containing or involving or occurring in the form ofpositively or negatively charged ions, i.e., charged moieties.“Nonionic” means comprising substantially of molecules with no formalcharges. Nonionic does not imply that there are no ions of any kind, butrather that a substantial amount of basic nitrogens are in anunprotonated state. “Salts” as used herein are compounds with no netcharge formed from positively and negatively charged ions. For purposesof this disclosure, “ionic liquids” are salts that are liquid below 100°C.; such liquids are typically nonvolatile, polar and viscous. “Nonionicliquids” means liquids that do not consist primarily of molecules withformal charges such as ions. Nonionic liquids are available in a widerange of polarities and may be polar or nonpolar; they are typicallymore volatile and less viscous than ionic liquids.

“Ionic strength” of a solution is a measure of the concentration of ionsin the solution. Ionic compounds (I.e., salts), which dissolve in waterwill dissociate into ions, increasing the ionic strength of a solution.The total concentration of dissolved ions in a solution will affectimportant properties of the solution such as the dissociation orsolubility of different compounds. The ionic strength, I, of a solutionis a function of the concentration of all ions present in the solutionand is typically given by the equation (A),

$\begin{matrix}{I = {\frac{1}{2}{\sum\limits_{i = 1}^{n}\; {c_{i}z_{i}^{2}}}}} & (A)\end{matrix}$

in which c, is the molar concentration of ion i in mol/dm³, z_(i) is thecharge number of that ion and the sum is taken over all ions dissolvedin the solution. In non-ideal solutions, volumes are not additive suchthat it is preferable to calculate the ionic strength in terms ofmolality (mol/kg H₂O), such that ionic strength can be given by equation(B),

$\begin{matrix}{I = {\frac{1}{2}{\sum\limits_{i = 1}^{n}\; {m_{i}z_{i}^{2}}}}} & (B)\end{matrix}$

in which m_(i) is the molality of ion i in mol/kg H₂O, and z_(i) is asdefined in the previous paragraph.

A “polar” molecule is a molecule in which some separation occurs of thecentres of positive and negative charge (or of partial positive andpartial negative charge) within the molecule. Polar solvents aretypically characterized by a dipole moment. Ionic liquids are consideredto be polar solvents, even though a dipole may not be present, becausethey behave in the same manner as polar liquids in terms of theirability to solubilize polar solutes, their miscibility with other polarliquids, and their effect on solvatochromic dyes. A polar solvent isgenerally better than a nonpolar (or less polar) solvent at dissolvingpolar or charged molecules.

“Nonpolar” means having weak solvating power of polar or chargedmolecules. Nonpolar solvents are associated with either having little orno separation of charge, so that no positive or negative poles areformed, or having a small dipole moment. A nonpolar solvent is generallybetter than a polar solvent at dissolving nonpolar, waxy, or oilymolecules.

“Hydrophobicity” is a property of a molecule leading it to be repelledfrom a mass of water. Hydrophobic molecules are usually nonpolar andnon-hydrogen bonding. Such molecules tend to associate with otherneutral and nonpolar molecules. The degree of hydrophobic character of amolecule, or hydrophobicity, can be quantified by a log P value. The logP is the logarithm of the lipid-water partition coefficient, P, of amolecule. The lipid-water partition coefficient seeks to determine theratio of solubilities of a molecule in a lipid environment and ahydrophilic aqueous environment. The lipid-water partition coefficientis the equilibrium constant calculated as the ratio of the concentrationof the molecule in the lipid phase divided by the concentration of themolecule in the aqueous phase.

“Moderately hydrophobic” is used herein to refer to compounds that aremoderately or completely soluble in aqueous solutions of low ionicstrength but that are much less soluble or essentially insoluble inaqueous solutions of high ionic strength. Such compound may be liquidsor solids; they may be organic or inorganic. An example of a moderatelyhydrophobic compound is tetrahydrofuran.

Partition coefficients can be determined using n-octanol as a model ofthe lipid phase and an aqueous phosphate buffer at pH 7.4 as a model ofthe water phase. Because the partition coefficient is a ratio, it isdimensionless. The partition coefficient is an additive property of amolecule, because each functional group helps determine the hydrophobicor hydrophilic character of the molecule. If the log P value is small,the molecule will be miscible with (or soluble in) water such that thewater and molecule will form a single phase in most proportions. If thelog P value is large, the compound will be immiscible with (or insolublein) water such that a two-phase mixture will be formed with the waterand molecule present as separate layers in most proportions.

It is possible to theoretically calculate log P values for many organiccompounds because of the additive nature of the partition coefficientarising from the individual functional groups of a molecule. A number ofcomputer programs are available for calculating log P values. The log Pvalues described herein are predicted using ALOGPS 2.1 software, whichcalculates the log P value for a given molecule using nine differentalgorithms and then averages the values. This computational method isfully described by Tetko I. V. and Tanchuk V. Y. in J. Chem. Inf.Comput. Sci., 2002, 42, 1136-1145 and in J. Comput. Aid. Mol. Des.,2005, 19, 453-463, both of which are incorporated herein by reference.

In contrast to hydrophobicity, “hydrophilicity” is a property of amolecule allowing it to be dissolved in or miscible with a mass ofwater, typically because the molecule is capable of transiently bondingwith water through hydrogen bonding. Hydrophilic molecules are usuallypolar. Such molecules may thus be compatible with other polar molecules.Hydrophilic molecules may comprise at least one hydrophilic substituentwhich can transiently bond with water through hydrogen bonding.Hydrophilic substituents include amino, hydroxyl, carbonyl, carboxyl,ester, ether and phosphate moieties.

“Insoluble” refers to a poorly solubilized solid in a specified liquidsuch that when the solid and liquid are combined a heterogeneous mixtureresults. It is recognized that the solubility of an “insoluble” solid ina specified liquid might not be zero but rather it would be smaller thanthat which is useful in practice. The use of the terms “soluble”,“insoluble”, “solubility” and the like are not intended to imply thatonly a solid/liquid mixture is intended. For example, a statement thatthe additive is soluble in water is not meant to imply that the additivemust be a solid; the possibility that the additive may be a liquid isnot excluded.

“Miscibility” is a property of two liquids that when mixed provide ahomogeneous solution. In contrast, “immiscibility” is a property of twoliquids that when mixed provide a heterogeneous mixture, for instancehaving two distinct phases (i.e., layers).

As used herein, “immiscible” means unable to merge into a single phase.Thus two liquids are described as “immiscible” if they form two phaseswhen combined in a proportion. This is not meant to imply thatcombinations of the two liquids will be two-phase mixtures in allproportions or under all conditions. The immiscibility of two liquidscan be detected if two phases are present, for example via visualinspection. The two phases may be present as two layers of liquid, or asdroplets of one phase distributed in the other phase. The use of theterms “immiscible”, “miscible”, “miscibility” and the like are notintended to imply that only a liquid/liquid mixture is intended. Forexample, a statement that the additive is miscible with water is notmeant to imply that the additive must be a liquid; the possibility thatthe additive may be a solid is not excluded.

As used herein, the term “contaminant” refers to one or more compoundsthat is intended to be removed from a mixture and is not intended toimply that the contaminant has no value.

As used herein, the term “salt” refers to an ionic compound that is nota zwitterion. This may include sodium chloride (traditional table salt),other inorganic salts, or salts in which the anion(s), the cation(s), orboth are organic. The term “salty” means comprising at least one salt.

As used herein the term “emulsion” means a colloidal suspension of aliquid in another liquid. Typically, an emulsion refers a suspension ofhydrophobic liquid (e.g., oil) in water whereas the term “reverseemulsion” refers to a suspension of water in a hydrophobic liquid.

As used herein the term “suspension” means a heterogeneous mixture offine solid particles suspended in liquid.

As used herein the term “foam” means a colloidal suspension of a gas ina liquid.

As used herein the term “dispersion” means a mixture of two components,wherein one component is distributed as particles, droplets or bubblesin the other component, and is intended to include emulsion (i.e.,liquid in liquid, liquid in supercritical fluid, or supercritical fluidin liquid), suspension (i.e., solid in liquid) and foam (i.e., gas inliquid).

“NMR” means Nuclear Magnetic Resonance. “IR spectroscopy” means infraredspectroscopy. “UV spectroscopy” means ultraviolet spectroscopy.

The term “DBU” means 1,8-diazabicyclo-[5.4.0]-undec-7-ene. The term“DMAE” means N,N-(dimethylamino)ethanol. The term “MDEA” means N-methyldiethanol-amine. The term “TMDAB” meansN,N,N′,N′-tetramethyl-1,4-diaminobutane. The term “TEDAB” meansN,N,N′,N′-tetraethyl-1,4-diaminobutane. The term “THEED” meansN,N,N′,N′-tetrakis(2-hydroxyethyl) ethylenediamine. The term “DMAPAP”means 1-[bis[3-(dimethylamino)]propyl]amino]-2-propanol. The term“HMTETA” means 1,1,4,7,10,10-hexamethyl triethylenetetramine. Structuralformulae for these compounds are shown in FIG. 2.

The term “wastewater” means water that has been used by a domestic orindustrial activity and therefore now includes waste products.

As used herein, “PEI” means branched or linear polyethyleneimines ofvarious molecular weights, including, but not limited to, methylatedpolyethyleneimine (“MPEI”) ethylated polyethyleneimine (“EPEI”),propylated polyethyleneimine (“PPEI”), and butylated polyethyleneimine(“BPEI”).

As used herein, “PMMA” refers to polymethyl methacrylate based polymersincluding, but not limited to, 3-(dimethylamino)-1-propylaminefunctionalized PMMA of various molecular weights.

As used herein, “PAA” refers to polyacrylic acid based polymersincluding, but not limited to, 3-(dimethylamino)-1-propylaminefunctionalized PAA of various molecular weights.

As used herein, “PMMA/PS” refers to poly(methylmethacrylate-co-styrene), which may be functionalized with, for example,3-(dimethylamino)-1-propylamine.

US Patent Application Publication No. 2008/0058549 discloses a solventthat reversibly converts from a nonionic liquid mixture to an ionicliquid upon contact with a selected trigger, such as CO₂. The nonionicliquid mixture includes an amidine or guanidine or both, and water,alcohol or a combination thereof.

Zhou K., et al, “Re-examination of Dynamics of Polyelectrolytes inSalt-Free Dilute solutions by Designing and Using a NovelNeutral-Charged-Neutral Reversible Polymer” Macromolecules (2009) 42,7146-7154, discloses a polymer that can undergo aneutral-charged-neutral transition in DMF with 5% water. The transitionbetween the neutral and charged state is achieved by alternatelybubbling CO₂ and N₂ through a mixture containing the polymer.

Switchable Water

Provided herein is a liquid mixture comprising an aqueous component inwhich the ionic strength can be reversibly varied from a lower ionicstrength to a higher ionic strength by subjecting the mixture to atrigger. Put simply, such aspects provide water that can be reversiblyswitched between water-with-substantially-no-salt and salty-water, overand over with little or substantially no energy input. The term“switchable water” is used herein to refer to the aqueous componentwhich is pure water mixed with an additive, or an aqueous solution mixedwith an additive, wherein the additive can switch between an ionic formand a non-ionic form in order to increase or decrease the ionic strengthof the water or aqueous solution, respectively.

Traditionally, once a salt was added to water, high energy input wasrequired to recapture the water (e.g., since the salted water had to beheated to its boiling point). Accordingly, certain aspects of thisapplication provide methods of separating a compound from a mixture bysolubilizing the compound in an aqueous solution of a first ionicstrength (a switchable water) and then isolating the compound byswitching the medium to a solution of a second ionic strength. Suchmethods use non-ionic aqueous solutions and ionic liquids. Switchablewater can be reused over and over in the extraction of a desired orselected compound.

Aqueous mixtures including switchable water as described herein areuseful for extraction of a solute from a mixture, a solution, or amatrix. After use in its lower ionic strength form for example, forextraction of a water soluble solute, the switchable water is triggeredto switch to its higher ionic strength form, to cause the precipitationor separation of the solute. The switchable water can then be re-used byswitching it back to the lower ionic strength form. Solutes forextraction are either pure compounds or mixtures of compounds. Theyinclude both contaminants and desired materials. Such solutes can beextracted from various compositions, including, without limitation,soil, clothes, rock, biological material (for example, wood, pulp,paper, beans, seeds, meat, fat, bark, grass, crops, fur, natural fibres,cornstalks, oils), water, equipment, or manufactured materials (forexample, machined parts, molded parts, extruded material, chemicalproducts, refined oils, refined fuels, fabrics, fibres, sheets, and likematerials, whether made of metal, mineral, plastic, inorganic, organic,or natural materials or combinations thereof). Desired solutes to beextracted include, without limitation, medicinal compounds, organiccompounds, intermediate compounds, minerals, synthetic reagents, oils,sugars, foods, flavorants, fragrances, dyes, pesticides, fungicides,fuels, spices, and like materials.

Other non-limiting examples of selected solutes include the following:plant extracts (e.g., lignin, cellulose, hemicellulose, pyrolysisproducts, leaf extracts, tea extracts, petal extracts, rose hipextracts, nicotine, tobacco extracts, root extracts, ginger extracts,sassafras extracts, bean extracts, caffeine, gums, tannins,carbohydrates, sugars, sucrose, glucose, dextrose, maltose, dextrin);other bio-derived materials (e.g., proteins, creatines, amino acids,metabolites, DNA, RNA, enzymes); alcohols, methanol, ethanol,1-propanol, 1-butanol, 2-propanol, 2-butanol, 2-butanol, t-butanol,1,2-propanediol, glycerol, and the like; products of organic synthesis(e.g., ethylene glycol, 1,3-propanediol, polymers, poly(vinyl alcohol),polyacrylamides, poly(ethylene glycol), poly(propylene glycol));industrially useful chemicals (e.g., plasticizers, phenols,formaldehyde, paraformaldehyde, surfactants, soaps, detergents,demulsifiers, anti-foam additives); solvents (e.g., THF, ether, ethylacetate, acetonitrile, dimethylsulfoxide, sulfolene, sulfolane,dimethylformamide, formamide, ethylene carbonate, propylene carbonate,dimethylacetamide, hexamethylphosphoramide); fossil fuel products (e.g.,creosote, coal tar, coal pyrolysis oil components, crude oil,water-soluble components of crude oil); colorants (e.g., dyes, pigments,organic pigments, stains, mordants); undesired compounds and mixtures(e.g., dirt or stains on clothing or equipment).

Selected compounds that may be suited to extraction methods describedherein include compounds that are soluble to different degrees in waterof lower ionic strength and water of higher ionic strength. Certainselected solutes are more soluble in aqueous solutions as describedherein that have lower ionic strength and include an amine additive thanthey are in neat water. Because the following description is about areversible reaction that proceeds from low ionic strength to high ionicstrength and back again, over and over, one must choose one of these twostates to begin the process. However, this choice is arbitrary, and asdescribed below, one could start with either state depending on thespecific application.

Switchable Additive

The exemplary description provided below starts with the low ionicstrength switchable water, which comprises water and a switchableadditive in its non-ionic form that is substantially soluble in water.The switchable water with the non-ionic form of the additive has a lowerionic strength than the switchable water with the ionic form of theadditive. In specific embodiments, where the switchable additive doesnot contain other ionized functional groups, the switchable water withthe non-ionic form of the additive has little to no ionic strength.

The switchable water can be used as a solvent to dissolve compounds thatdo not react with the additive. When it is desirable to separatedissolved compounds from the non-ionic switchable water, a trigger isapplied and the additive is converted to its ionic form. The resultantionic switchable water has a higher ionic strength.

In accordance with one example, both the non-ionic and the ionic formsof the switchable additive employed in this reversible reaction aresoluble with water, such that where a liquid mixture separates into twophases, a hydrophobic phase and an aqueous phase, substantially all ofthe additive remains in the aqueous layer, no matter whether it is inits non-ionic form or its ionic form. In this example, in contrast tothe additive, certain compounds will no longer be soluble in the higherionic strength solution, and they will separate into a phase that isdistinct from the ionic aqueous phase. This distinct phase may be apre-existing hydrophobic liquid phase (non-aqueous solvent).

In accordance with an alternative example, only the ionic form of theswitchable additive is substantially soluble in water, such that whenthe additive is converted to its non-ionic form, two phases are formed,with the non-ionic form of the additive being largely or completely inthe non-aqueous phase. The non-aqueous phase can include only thenon-ionic form of the switchable additive, or it can include a solventthat is not soluble or miscible with water, such as a pre-existinghydrophobic liquid phase (non-aqueous solvent). In many cases, thenon-aqueous phase will comprise some water, although in manyapplications the amount of water in the non-aqueous phase wouldpreferably be as low as possible.

The switchable additive (also referred to herein as an “additive”) is acompound comprising an amine nitrogen that is sufficiently basic thatwhen it is in the presence of water and CO₂ (which form carbonic acid),for example, it becomes protonated. When an aqueous solution thatincludes such a switchable additive is subjected to a trigger, theadditive reversibly switches between two states, a non-ionic state wherethe amine nitrogen is trivalent and is uncharged, and an ionic statewhere the amine nitrogen is protonated making it a 4-coordinatepositively charged nitrogen atom. Accordingly, the charged amine moietyhas a negatively charged counterion that is associated with it insolution. The nature of the counterion depends on the trigger used andwill be described below. An aqueous solution comprising the additive inits ionic state is distinguishable from an aqueous solution comprisingthe compound in its non-ionic state by comparing the ionic strengths.

The switchable additive is at least partially soluble in water when inits ionic form. Specifically, the switchable additive must besufficiently soluble in water when in its ionic form to impart anincrease in ionic strength in comparison to the ionic strength of thewater (or aqueous solution depending on the application) without theionic form of the additive present.

In certain embodiments, the switchable water comprises water and anamine additive that is peralkylated. The term “peralkylated” as usedherein means that the amine has alkyl or other groups connected tonitrogen atoms that are sufficiently basic that they are protonated bycarbonic acid, so that the molecule contains no N—H bonds. Aminecompounds of formulae (1) and (4) which do not have any N—H bonds arepreferred because most primary and secondary amines are capable ofcarbamate formation during switching with CO₂. Removal of carbamate ionsin water by heating and bubbling with a flushing gas to switch the saltback to the amine form can be difficult. This is evident fromcomparative example 2, in which it was determined that it was notpossible to switch certain primary and a secondary amine additives inionic form back to the corresponding non-ionic amine forms using lowenergy input triggers. Thus, carbamate formation is undesirable becauseit can decrease the efficiency of reverting an ionic solution back to anaqueous solution of amine (non-ionic form). This concern about formationof carbamate ions is not relevant if the amine is an aniline (i.e., anaryl or heteroaryl group is attached directly to a nitrogen atom); insuch a molecule, an N—H bond is not considered unpreferred.

Stable carbamate formation can be greatly reduced by using bulkysubstituents on primary and secondary amines to provide steric hindrance(Bougie F. and Illiuta M. C., Chem Eng Sci, 2009, 64, 153-162 andreferences cited therein). Steric hindrance allows for easier CO₂desorption. Tertiary amines are preferred since their ionic forms do notinclude carbamates but rather are bicarbonates anions. However, in someembodiments, primary and secondary amines that have bulky substituentsare preferred because the switching process may be faster than thatobserved with tertiary amines. As demonstrated in Example 22 below, theinventors reasonably expect that efficient reversible switching ispossible between non-ionic and ionic forms with primary and secondaryamines that have bulky substituents. The inventors also reasonablyexpect that the presence of a small amount of a secondary or primaryamine that is capable of carbamate formation, in addition to aswitchable additive compound of formula (1), would not inhibit switchingof the additive. In some embodiments, the presence of a small amount ofsecondary or primary amine may increase the rate of switching of theadditive between its ionic and non-ionic forms.

In one embodiment, a primary amine additive can be used. However, thereversion of the ionic form of the primary amine additive to thenon-ionic form is too difficult to be of practical use in applicationwhere reversion is required. Rather, a primary amine additive can bevaluable in situations in which reversal of the additive ionization isunnecessary. Alternatively, a primary amine additive can be valuable insituations in which the use of higher temperatures, longer reactiontimes or other more severe conditions to force the reversion to takeplace are acceptable.

In another embodiment, a secondary amine additive can be used. Asdemonstrated in Example 22, certain secondary amine additives arereversibly switchable between an ionized and a non-ionized form.

Useful additives can comprise more than one nitrogen centre. Suchcompounds are called, for example, diamines, triamines, tetraamines orpolyamines. Polyamines include polymers with nitrogens in the polymerbackbone. Polyamines also include polymers with nitrogens in pendantgroups, for example, biopolymers and derivatives thereof. Polyaminesalso include polymers with nitrogens in the polymer backbone and withnitrogens in pendant groups. Polyamines also include small molecules(i.e., not polymers) that have more than one nitrogen atom. Examples ofpolyamines include poly(vinylamine), poly(N-vinyl-N,N-dimethylamine),poly(allylamine) poly(N-allyl-N,N-dimethylamine),1,2,3,4,5,6-hexakis(N,N-dimethylaminomethyl)benzene (e.g., C₆(CH₂NMe₂)₆)and 1,2,3,4,5,6-hexakis(N,N-dimethylaminomethyl)cyclohexane (e.g.,C₆H₆(CH₂NMe₂)₆).

In a specific example, the additive is a biopolymer comprising one ormore amine nitrogens that are sufficiently basic that when in thepresence of water and CO₂ (which form carbonic acid), for example, itbecomes protonated. Examples of suitable biopolymers for use as aswitchable additive include, but are not limited to, collagens(including Types I, II, III, IV, V and VI), denatured collagens (orgelatins), fibrin-fibrinogen, elastin, glycoproteins, polysaccharidessuch as, but not limited to, alginate, chitosan, N-carboxymethylchitosan, O-carboxymethyl chitosan, N,O-carboxymethyl chitosan,hyaluronic acid, chondroitin sulphates and glycosaminoglycans (orproteoglycans), oxidized polysaccharides such as, but not limited tooxidized chondroitin sulphate, oxidized alginate and oxidized hyaluronicacid. In each case, the biopolymer can be derivatised to incorporateamine nitrogens that are sufficiently basic that when in the presence ofwater and CO₂ (which form carbonic acid), for example, it becomesprotonated.

An example of a method to prepare polyamine additive includes reactinghomopolymers of propylene oxide or ethylene oxide with maleic anhydrideunder free radical conditions either in solution or in solid state toyield grafted material. As an alternative to homopolymers, random orblock copolymers of propylene oxide and ethylene oxide can be used. Onceprepared, the grafted material is reacted with a diamine (e.g.,3-dimethylamino-1-propylamine) to form a polyamine additive that isuseful as an additive in embodiments of the invention described herein.In some embodiments, ratios of the ethylene oxide and propylene oxiderepeating units of the polyamine are controlled such that, at a giventemperature and pressure, the additive in its “off” state issubstantially insoluble in water and in its “on” state is soluble inwater.

Another example of a method to prepare polyamine additive includesreacting a polymer of acrylic acid (or a corresponding ester) with adiamine (e.g., 3-dimethylamino-1-propylamine) to form the additive viaamide bond formation. As an alternative to acrylic acid polymer, anotherpolymer that comprises carboxylic acid (or a corresponding esterthereof) can be used. An example of such a polymer includes a random orblock co-polymer of polystyrene and a polymer comprising carboxylic acidand/or ester. The amide bond is formed, for example, via dehydration,alcohol elimination, alkoxide elimination, acid chloride reaction,catalytically, or the like. Any secondary or primary amide nitrogen atomcan be alkylated to further tune solubility properties of the additive.In some embodiments, ratios of the components of the polyamine arecontrolled such that, at a given temperature and pressure, the additivein its “off” state is substantially insoluble in water and in its “on”state, after exposure to CO₂ and H₂O, is soluble in water.

Specific, non-limiting examples of amine containing polymers useful asswitchable water additives are: branched or linear polyethyleneimines(“PEIs”) of various molecular weights, including, functionalized PEIssuch as, methylated polyethyleneimine (“MPEI”), ethylatedpolyethyleneimine (“EPEI”), propylated polyethyleneimine (“PPEI”), andbutylated polyethyleneimine (“BPEI”); functionalized polymethacrylate(“PMA”) polymers of various molecular weights; functionalizedpoly(methyl acrylate) (“PMeA”) polymers of various molecular weights;functionalized polymethyl methacrylate (“PMMA”) polymers including, butnot limited to, 3-(dimethylamino)-1-propylamine functionalized PMMA ofvarious molecular weights; functionalized polyacrylic acid (“PAA”)polymers including, but not limited to, 3-(dimethylamino)-1-propylaminefunctionalized PAA of various molecular weights; and functionalizedpoly(methyl methacrylate-co-styrene) (“PMMA/PS”) copolymers including,but not limited to 3-(dimethylamino)-1-propylamine functionalizedPMMA/PS of various molecular weights and mol % styrenic units. The term“functionalized”, as used herein with reference to polymers, meanspolymers that comprise one or more functional groups, such as, but notlimited to, substituted or unsubstituted aliphatic groups. In certainembodiments the polymers are functionalized to include protonatablenitrogen atoms. As would be well understood by a worker skilled in theart, a functionalized polymer can be synthesized by functionalizing apolymer at pendant reactive groups (e.g., acid groups) to add thedesired functional group or groups. In a specific example of thisalternative, polymers are further functionalized at existing primaryamines to form secondary or tertiary amines. Alternatively, thefunctionalized polymer can be synthesized from monomers, or mixture ofmonomers, that contain the desired functional group or groups.

When referring to polymers herein, the terminology used refers to“functionalized” polymers without specifying the bonds formed as aresult of incorporation of the functional groups in the polymer. Forexample, the polyacrylamide formed from the reaction of a PAA with anamine is, for simplicity, referred to herein as a “functionalized PAA”.

In certain embodiments the additive is immiscible or insoluble, orpoorly miscible or poorly soluble, in water but is converted by atrigger to a form that is ionic and is at least partially soluble ormiscible with water. In order to function as a switchable additive, theadditive must be sufficiently soluble in water or an aqueous solutionwhen in the “on” or “ionized form” so that the ionized additive impartsan increase in ionic strength of the water or aqueous solution withoutthe additive or with the additive in the “off” or “non-ionized” form.The immiscibility or insolubility of the additive in its non-ionizedform is advantageous in some applications because the additive can bereadily removed from the water, when such removal is desired, by theremoval of the trigger. TEDAB is an example of an additive thatfunctions according to this embodiment.

Also provided herein are ionic polymers, which are salts formed from asimple acid-base reaction between a polymer having pendant acidic groupsand amine or amidine-containing molecules having an accessible basicgroup (for example a diamine- or triamine-containing compound). The“non-ionized”, or “off” form of these ionic polymers is actuallypartially ionized, which can result in increase water solubility of the“non-ionized” form of these polymers, in comparison to the non-ionizedform of the functionalized polymers described above. For example, abasic diamine can undergo an acid-base reaction with a polymercontaining an acidic side group to yield a singly ionic polymer in theoff form. This polymer can then undergo a second reaction with carbonicacid, for example, to give a doubly ionic polymer in the on form.

In certain embodiments, the water solubility or miscibility of apolymeric additive in water can be switched by taking advantage of theupper and/or lower critical solution temperatures of the polymericadditive. In the present situation the lower critical solutiontemperature (or LCST) is the critical temperature below which thepolymer is soluble or miscible in water or an aqueous solution and theupper critical solution temperature (or UCST) is the criticaltemperature above which the polymer is soluble or miscible in water. Forthose polymeric additives that have an LCST in the non-ionized form,temperature can be used to facilitate removal of the additive fromwater. After the polymeric additive is switched from its ionized form toits non-ionized form, the temperature is raised to above the LOST suchthat the polymeric additive either precipitates or becomes immisciblewith the water or aqueous solution of the system. The polymeric additivecan then be removed from the water using standard techniques such asfiltration or decanting.

In certain aspects the additive is a compound of formula (1),

where R¹, R², and R³ are independently:

H;

a substituted or unsubstituted C₁ to C₈ aliphatic group that is linear,branched, or cyclic, optionally wherein one or more C of the alkyl groupis replaced by a {—Si(R¹⁰)₂—O—} unit up to and including 8 C units beingreplaced by 8 {—Si(R¹⁰)₂—O—} units;

a substituted or unsubstituted C_(n)Si_(m) group where n and m areindependently a number from 0 to 8 and n+m is a number from 1 to 8;

a substituted or unsubstituted C₄ to C₈ aryl group wherein aryl isoptionally heteroaryl, optionally wherein one or more C is replaced by a{—Si(R¹⁰)₂—O—} unit;

a substituted or unsubstituted aryl group having 4 to 8 ring atoms,optionally including one or more {—Si(R¹⁰)₂—O—} unit, wherein aryl isoptionally heteroaryl;

a —(Si(R¹⁰)₂—O)_(p)— chain in which p is from 1 to 8 which is terminatedby H, or is terminated by a substituted or unsubstituted C₁ to C₈aliphatic and/or aryl group;

a substituted or unsubstituted C₁ to C₈ aliphatic-C₄ to C₈ aryl groupwherein aryl is optionally heteroaryl, optionally wherein one or more Cis replaced by a {—Si(R¹⁰)₂—O—} unit; or

wherein R¹⁰ is a substituted or unsubstituted C₁ to O₈ aliphatic group,C₁ to O₈ alkoxy, or C₄ to C₈ aryl wherein aryl is optionally heteroaryl.

A substituent may be independently: alkyl; alkenyl; alkynyl; aryl;aryl-halide; heteroaryl; cycloalkyl (non-aromatic ring); Si(alkyl)₃;Si(alkoxy)₃; halo; alkoxyl; amino, which includes diamino; alkylamino;alkenylamino; amide; amidine; hydroxyl; thioether; alkylcarbonyl;alkylcarbonyloxy; arylcarbonyloxy; alkoxycarbonyloxy;aryloxycarbonyloxy; carbonate; alkoxycarbonyl; aminocarbonyl;alkylthiocarbonyl; phosphate; phosphate ester; phosphonato; phosphinato;cyano; acylamino; imino; sulfhydryl; alkylthio; arylthio;thiocarboxylate; dithiocarboxylate; sulfate; sulfato; sulfonate;sulfamoyl; sulfonamide; nitro; nitrile; azido; heterocyclyl; ether;ester; silicon-containing moieties; thioester; or a combination thereof.The substituents may themselves be substituted. For instance, an aminosubstituent may itself be mono or independently disubstituted by furthersubstituents defined above, such as alkyl, alkenyl, alkynyl, aryl,aryl-halide and heteroaryl cyclyl (non-aromatic ring).

A substituent may be preferably at least one hydrophilic group, such asSi(C₁-C₄-alkoxy)₃, C₁-C₄-alkoxyl, amino, C₁-C₄-alkylamino,C₂-C₄-alkenylamino, substituted-amino, C₁-C₄-alkyl substituted-amino,C₂-C₄-alkenyl substituted-amino amide, hydroxyl, thioether,C₁-C₄-alkylcarbonyl, C₁-C₄-alkylcarbonyloxy, C₁-C₄-alkoxycarbonyloxy,carbonate, C₁-C₄-alkoxycarbonyl, aminocarbonyl, C₁-C₄-alkylthiocarbonyl,phosphate, phosphate ester, phosphonato, phosphinato, acylamino, imino,sulfhydryl, C₁-C₄-alkylthio, thiocarboxylate, dithiocarboxylate,sulfate, sulfato, sulfonate, sulfamoyl, sulfonamide, nitro, nitrile,C₁-C₄-alkoxy-C₁-C₄-alkyl, silicon-containing moieties, thioester, or acombination thereof.

In some embodiments, compounds of formula (1) are water-soluble orwater-miscible. In alternative embodiments, compounds of formula (1) arewater-insoluble or water-immiscible, or only partially water-soluble orwater-miscible.

In certain embodiments, each of R¹, R² and R³ may be substituted by atertiary amine, which is optionally sufficiently basic to becomeprotonated when it is in the presence of water and CO₂ (which formcarbonic acid).

The present application further provides an ionic solution comprisingwater and a salt additive of formula (2) where R′, R², and R³ are asdefined for the compound of formula (1) and E is O, S or a mixture of Oand S,

In some embodiments, a compound of formula (2) is prepared by a methodcomprising contacting a compound of formula (1) with CO₂, CS₂ or COS inthe presence of water, thereby converting the compound to the salt offormula (2). In some embodiments, a compound of formula (2) is watersoluble.

Any of R¹, R², and R³ of the salt of formula (2) may be optionallysubstituted as discussed for the compound of formula (1). However,should the optional substituent comprise a nitrogen of sufficientbasicity to be protonated by carbonic acid, it can be present in itsprotonated form as it may be protonated by the ionizing trigger. Forinstance, if the optional substituent is an amino group, such as atertiary amino group, this may exist as a quaternary ammonium moiety inthe salt of formula (2).

The present application further provides a switchable water comprisingwater and a salt of formula (3). In a preferred embodiment, in thepresence of water and CO₂, an amine compound of formula (1), converts toan ammonium bicarbonate, depicted as a salt of formula (3) as shownbelow

where R¹, R², and R³ areas defined above. In some embodiments, acompound of formula (3) is water soluble. There may be some carbonateanions present, in addition to bicarbonate anions. As would be readilyunderstood by a worker skilled in the art, under appropriate conditionsthe ⁻O₃CH can lose a further hydrogen atom to form ²⁻O₃C (carbonate)and, thereby, protonate a second additive. In a specific embodiment, theionic form of protonated additive comprises a bicarbonate ion. In analternative embodiment the ionic form of the additive comprises twoprotonated amines and a carbonate ion. Given that the acid-base reactionis an equilibrium reaction, both the carbonate ion and the bicarbonateion may be present with protonated additive ions.

Should an optional substituent comprise a basic nitrogen, it may bepresent in protonated form if it can be protonated by carbonic acid. Forinstance, if the optional substituent is an amino group, such as atertiary amino group, this may exist as a quaternary ammonium moiety inthe salt of formula (3).

A water-soluble additive of formula (1) can provide a switchable waterthat is a single-phase mixture and can function as a solvent forwater-soluble substances. Although in theory an aqueous solution of thewater-soluble compound of formula (1), in the absence of othercomponents, will have an ionic strength of zero since no charged speciesare present; in practice, the ionic strength might be small but higherthan zero due to some impurities such as dissolved air or small amountsof salts. Because of the zero or small ionic strength, a switchablewater comprising a water-miscible compound of formula (1) isparticularly useful as a solvent for substances which are miscible orsoluble in low ionic strength aqueous solutions.

In some embodiments, both the non-ionic additive of formula (1) and thesalt additive formula (2) are water-soluble and can each, therefore,form a single phase aqueous solution when dissolved in water. This meansthat the non-ionic compound of formula (1) and the salt of formula (2)can remain in aqueous solution as a single phase with water afterswitching. Switching a non-ionic switchable water comprising thecompound of formula (1) to an ionic switchable water comprising the saltof formula (2) increases the ionic strength of the switchable water.Increasing the ionic strength of the switchable water can be used toexpel a dissolved substance which is insoluble in such an increasedionic strength solution without the need for distillation or otherenergy intensive separation techniques.

Alternatively water-insoluble, or poorly soluble, additive of formula(1) can provide a switchable water that is a two-phase mixture. Althoughin theory the water in the two-phase mixture, in the absence of othercomponents, will have a zero or very low ionic strength because nocharged species are present in significant quantities (charged speciespresent in small concentrations may include the H⁺ and OH⁻ ions that onewould expect from the dissociation of water and the amount of protonatedadditive formed by the reaction of additive with water); in practice,the ionic strength might also be slightly increased by the presence ofsome impurities such as dissolved air or small amounts of salts. Becauseof the zero or small ionic strength, a switchable water mixturecomprising a water-immiscible, or poorly miscible additive of formula(1) is particularly useful as a solvent for substances which aremiscible or soluble in low ionic strength aqueous solutions.

In some embodiments, the non-ionic additive of formula (1) iswater-insoluble, or poorly soluble, and the salt additive formula (2) iswater-soluble such that a single phase is formed only when the additiveis switched to its ionic form. Switching a non-ionic switchable watercomprising the compound of formula (1) to an ionic switchable watercomprising the salt of formula (2) increases the ionic strength of theswitchable water. In this embodiment, the fact that the non-ionic formof the additive is water-insoluble or immiscible, can be useful insituations where it is beneficial to remove the additive from theaqueous phase following switching to the non-ionic form.

In accordance with either embodiment, the salt of formula (2) can beswitched back into a non-ionic additive of formula (1) by removal of theionizing trigger, such as CO₂, or by addition of a non-ionizing trigger.This is advantageous because it allows the re-use of the switchablewater.

In certain embodiments, at least one of R¹, R² and R³ can be replaced byone or more further tertiary amine groups. For instance, R¹ may besubstituted with a tertiary amine, which may itself be furthersubstituted with a tertiary amine. Thus, the present invention includesthe use of an aqueous solution comprising water and a compound offormula (4),

where R², and R³, are independently as defined for the compound offormula (1);

R⁵ and R⁶ are independently selected from the definitions of R¹, R² andR³ of formula (1);

R⁴ is a divalent bridging group selected from a substituted orunsubstituted O₁ to C₈ alkylene group that is linear, branched orcyclic; a substituted or unsubstituted C₂ to C₈ alkenylene group that islinear, branched or cyclic; a substituted or unsubstituted —C_(n)Si_(m)—group where n and m are independently a number from 0 to 8 and n+m is anumber from 1 to 8; a substituted or unsubstituted C₅ to C₈ arylenegroup optionally containing 1 to 8 {—Si(R¹⁰)₂—O—} units; a substitutedor unsubstituted heteroarylene group having 4 to 8 atoms in the aromaticring optionally containing 1 to 8 {—Si(R¹⁰)₂—O—} units; a—(Si(R¹⁰)₂—O)_(p)— chain in which “p” is from 1 to 8; a substituted orunsubstituted C₁ to C₈ alkylene-C₅ to C₈ arylene group optionallycontaining 1 to 8 {—Si(R¹⁰)₂—O—} units; a substituted or unsubstitutedC₂ to C₈ alkenylene-C₅ to C₈ arylene group optionally containing 1 to 8{—Si(R¹⁰)₂—O—} units; a substituted or unsubstituted C₁ to C₈alkylene-heteroarylene group having 4 to 8 atoms in the aromatic ringoptionally containing 1 to 8 {—Si(R¹⁰)₂—O—} units; a substituted orunsubstituted C₂ to C₈ alkenylene-heteroarylene group having 4 to 8atoms in the aromatic ring optionally containing 1 to 8 {—Si(R¹⁰)₂—O—}units; R¹⁰ is a substituted or unsubstituted C₁ to C₈ alkyl, C₈ to C₈aryl, heteroaryl having from 4 to 8 carbon atoms in the aromatic ring orC₁ to C₈ alkoxy moiety; and “a” is an integer. In some embodiments,compounds of formula (4) are water-soluble. Additives with large valuesof “a” are likely to be more effective in increasing the ionic strengthwhen they are in their ionic forms but may suffer from poor solubilityin water when they are in their non-ionic forms. For the avoidance ofdoubt, it is pointed out that when “a”>0, in a repeat unit —N(R⁵)—R⁴—,R⁴ and R⁵ may have a different definition from another such repeat unit.

In some embodiments, the additive is an oligomer or a polymer thatcontains one or more than one nitrogen atom(s) that is sufficientlybasic to be protonated by carbonic acid in the repeating unit of theoligomer or polymer. In accordance with one embodiment, the nitrogenatoms are within the backbone of the polymer. The additive of formula(4) is a specific example of such a polymer in which the nitrogenatom(s) are within the backbone of the polymer. In alternativeembodiments, the additive is an oligomer or polymer that contains one ormore than one nitrogen atom(s) that is sufficiently basic to beprotonated by carbonic acid in a pendant group that is part of therepeating unit, but that is not situated along the backbone of theoligomer or polymer. In some embodiments, some or all of the nitrogenatom(s) that are sufficiently basic to be protonated by carbonic acidare amidine groups. Such amidine groups may be part of the backbone ofthe oligomer or polymer or may be in pendant group s that are part ofthe repeating unit.

Example polymer additives having formulae (5a-g) are shown below. Inthese formulae, “n” refers to the number of repeat units containing atleast one basic group and “m” refers to the number of repeat unitscontaining no basic group. Additives with large values of “n” are likelyto be more effective in increasing the ionic strength when they are intheir ionic forms but may have poor solubility in water when they are intheir non-ionic forms. It is not necessary that the backbone of thepolymer be entirely made of carbon and hydrogen atoms; in someembodiments, the backbone may comprise other elements. For example, thepolymer may have a polysiloxane backbone with amine-containing sidegroups, a polyether backbone with amine-containing side groups, or thebackbone can itself comprise amine groups. In some embodiments, it ispreferably to have a backbone or side groups that is reasonablyhydrophilic or polar. Without wishing to be bound by theory, it iscontemplated that a hydrophilic or polar backbone or side groups canhelp the charged form of the additive from precipitating.

R¹ can be substituted with a tertiary amine, which may itself be furthersubstituted with a tertiary amine, as shown in the compound of formula(4). Such tertiary amine sites may be protonated when contacted withCO₂, CS₂ or COS in the presence of water. Thus, in certain embodimentsthe present invention provides an ionic solution comprising water and asalt of formula (4).

It will be apparent that when the polymer additive is in its ionizedform, in order to balance the positive charges on the quaternaryammonium sites in the cation, a number of anions equivalent to thenumber of protonated basic sites should be present. For example, in theionized form of the polymer additive of formula (4), there will be (a+1)⁻E₃CH anionic counterions for each cation having (a+1) quaternaryammonium sites in the salt of formula (4). Alternatively, some of the⁻E₃CH ions are replaced by anions of formula CE₃ ²⁻.

Each of R¹, R², and R³ in the compound of formula (1) can be substitutedwith a tertiary amine which may itself be further substituted with atertiary amine. Such tertiary amine sites may be protonated whencontacted with CO₂, CS₂ or COS in the presence of water. However, notall amine compounds having more than one amine site (i.e. polyamines)may be capable of protonation by the trigger at every amine site. Thus,amine compounds of formula (4) may not be protonated at every tertiaryamine site when contacted with CO₂, COS or CS₂. Consequently, it shouldnot be assumed that all basic sites must be protonated in order toeffectively raise the ionic strength of the switchable water.

Furthermore, the pK_(aH) (i.e. the pK_(a) of the conjugate acid (i.e.,ionic form)) of the amine compound of formula (1) should not be so highas to render the protonation irreversible. In particular, the ionic formof the additive should be capable of deprotonation through the action ofthe non-ionizing trigger (which is described below to be, for example,heating, bubbling with a flushing gas, or heating and bubbling with aflushing gas). For example, in some embodiments, the pK_(aH) is in arange of about 6 to about 14. In other embodiments, the pK_(aH) is in arange of about 7 to about 13. In certain embodiments the pK_(aH) is in arange of about 7.8 to about 10.5. In some embodiments, the pK_(aH) is ina range of about 8 to about 10.

Additives useful in a switchable water can have higher aliphatic (C₅-C₈)and/or siloxyl groups. Monocyclic, or bicyclic ring structures, can alsobe used. A higher number of aliphatic groups can cause a compound to bewaxy and water-immiscible at room temperature. As described above, thismay be advantageous if it means that the non-ionic form of the additiveis water-immiscible, but the ionic form is water miscible.

In certain embodiments, the additive is liquid at room temperature.

It is preferred that the aliphatic and/or siloxyl chain length is 1 to6, more preferably 1 to 4. A siloxyl group contains {—Si(R¹⁰)₂—O—}units; where R¹⁰ is a substituted or unsubstituted C₁ to C₈ alkyl, C₅ toC₈ aryl, heteroaryl having from 4 to 8 carbon atoms in the aromatic ringor C₁ to C₈ alkoxy moiety. Conveniently, in some discussions herein, theterm “aliphatic/siloxyl” is used as shorthand to encompass aliphatic,siloxyl, and a chain which is a combination of aliphatic and siloxylunits.

Optionally the additive comprises a group that includes an ether orester moiety. In preferred embodiments, an aliphatic group is alkyl.Aliphatic groups may be substituted with one or more moieties such as,for example, alkyl, alkenyl, alkynyl, aryl, aryl halide, hydroxyl,heteroaryl, non-aromatic rings, Si(alkyl)₃, Si(alkoxy)₃, halo, alkoxy,amino, ester, amide, amidine, guanidine, thioether, alkylcarbonate,phosphine, thioester, or a combination thereof. Reactive substituentssuch as alkyl halide, carboxylic acid, anhydride and acyl chloride arenot preferred.

Strongly basic groups such as amidines and guanidines may not bepreferred if their protonation by carbonic acid is difficult to reverse.

In other embodiments of the invention, substituents are loweraliphatic/siloxyl groups, and are preferably small and non-reactive.Examples of such groups include lower alkyl (C₁ to C₄) groups. Preferredexamples of the lower aliphatic groups are CH₃, CH₂CH₃, CH(CH₃)₂,C(CH₃)₃, Si(CH₃)₃, CH₂CH₂OH, CH₂CH(OH)CH₃, and phenyl. Monocyclic, orbicyclic ring structures, may also be used.

It will be apparent that in some embodiments substituents R may beselected from a combination of lower and higher aliphatic groups.Furthermore, in certain embodiments, the total number of carbon andsilicon atoms in all of the substituents R¹, R², R³ and R⁴ (includingoptional substituents) of a water-soluble compound of formula (1) may bein the range of 3 to 20, more preferably 3 to 15.

Referring to FIG. 1, a chemical scheme and schematic drawing are shownfor a switchable ionic strength solvent system of a water-miscible amineadditive of formula (1) and water. The chemical reaction equation showsan additive (non-ionic form) which is an amine compound of formula (1)and water on the left hand side and an ionic form of the additive as anammonium bicarbonate salt of formula (3) on the right hand side. Thisreaction can be reversed, as indicated. The schematic shows the samereaction occurring in the presence of tetrahydrofuran (THF) wherein asingle-phase aqueous solution of an amine additive (e.g., a compound offormula (1)) that is water-miscible, water and THF is shown on the leftside under a blanket of N₂. A two phase (layered) mixture is shown onthe right side under a blanket of CO₂. The two phases being an aqueoussolution of the salt of formula (3) comprising ammonium bicarbonate andwater, and THF.

Referring to FIG. 2, structures of a number of compounds of formula (1)are provided. DMEA or DMAE is N,N-(dimethylamino)ethanol, which informula (1) has R¹ is methyl; R² is methyl; and R³ is C₂H₄OH). MDEA isN-methyl diethanolamine, which in formula (1) has R¹ is methyl; R² isC₂H₄OH; and R³ is C₂H₄OH). Both compounds, DMEA and MDEA, are monoamineshaving a single tertiary amine group. TMDAB isN,N,N′,N′-tetramethyl-1,4-diaminobutane, which in formula (1) has R¹ ismethyl; R² is methyl; R³ is C₄H₈N(CH₃)₂). THEED isN,N,N′,N′-tetrakis(2-hydroxyethyl)ethylenediamine, which in formula (1)has R¹ is C₂H₄OH; R² is C₂H₄OH; and R³ is C₂H₄N(C₂H₄OH)₂). CompoundsTMDAB and THEED are diamines having two tertiary amine groups. CompoundDMAPAP is a triamine, having three tertiary amine groups,1-[bis[3-(dimethylamino)]propyl]amino]-2-propanol, which in formula (1)has R¹ is methyl; R² is methyl; and R³ isC₃H₆N(CH₂CH(OH)CH₃)C₃H₆N(CH₃)₂). Compound HMTETA is a tetramine, havingfour tertiary amine groups, 1,1,4,7,10,10-hexamethyltriethylenetetramine, which in formula (1) has R¹ is methyl; R² ismethyl; and R³ is C₂H₄N(CH₃)C₂H₄N(CH₃)C₂H₄N(CH₃)₂). These compounds arediscussed further in the working examples.

Referring to FIG. 3, multiple ¹H NMR spectra are shown from a MDEAswitchability study carried out in D₂O at 400 MHz. This is discussed inExample 4 below.

Referring to FIG. 4, multiple ¹H NMR spectra are shown from a DMAEswitchability study carried out in D₂O at 400 MHz. This is discussed inExample 4 below.

Referring to FIG. 5, multiple ¹H NMR spectra are shown from a HMTETAswitchability study carried out in D₂O at 400 MHz. This is discussed inExample 4 below.

Referring to FIG. 6, multiple ¹H NMR spectra are shown from a DMAPAPswitchability study carried out in D₂O at 400 MHz. This is discussed inExample 4 below.

Referring to FIG. 7, conductivity spectra are shown for the responses toa CO₂ trigger over time the following solutions: 1:1 v/v H₂O:DMAE; 1:1v/v H₂O:MDEA; and 1:1 w/w H₂O:THEED. Experimental details are discussedin Example 5 below.

Referring to FIG. 8, conductivity spectra are shown for the responses of1:1 v/v H₂O:DMAE; 1:1 v/v H₂O:MDEA; and 1:1 w/w H₂O:THEED solutions,which had been switched with a CO₂ trigger, to the removal of CO₂ bynitrogen bubbling over time. Experimental details are discussed inExample 5 below.

Referring to FIG. 9, a plot of the degree of protonation of 0.5 Msolutions of DMAE and MDEA in D₂O and a 0.1 M aqueous solution of THEEDin D₂O resulting from exposure to a CO₂ trigger over time is shown. Thisis discussed in Example 6 below.

Referring to FIG. 10, a plot of the degree of deprotonation of 0.5 Msolutions of DMAE and MDEA in D₂O and a 0.1 M solution of THEED in D₂O,which have been switched with a CO₂ trigger, to the removal of thetrigger by nitrogen bubbling over time is shown. This is discussed inExample 6 below.

Referring to FIG. 11, conductivity spectra for the responses of 1:1 v/vH₂O: amine solutions to a CO₂ trigger over time, in which the amine isTMDAB (♦), HMTETA (▪), and DMAPAP (▴), is shown. This is discussed inExample 7 below.

Referring to FIG. 12, conductivity spectra for the responses of 1:1 v/vH₂O: amine solutions, which have been switched with a CO₂ trigger, tothe removal of the trigger by nitrogen bubbling over time, in which theamine is TMDAB (♦), HMTETA (▪), and DMAPAP (▴), are shown. This isdiscussed in Example 7 below.

Referring to FIG. 13, five photographs A-E representing different stagesof an experiment exhibiting how the switchable ionic strength characterof amine additive TMDAB can be used to disrupt an emulsion of water andn-decanol are shown. This is discussed in Example 8 below.

In accordance with an alternative aspect, the switchable additive is anamidine having formula (6):

where R¹, R², and R³ are each, independently, as defined above. Theionized form of the additive of formula (6) is:

where n is a number from 1 to 6 sufficient to balance the overall chargeof the amidinium cation, and E is O, S or a mixture of O and S.

Ionizing and Non-Ionizing Triggers

As used herein, a trigger is a change that leads to a chemical reactionor a series of chemical reactions. A trigger can either be an ionizingtrigger, which acts to effect conversion of the additive to its ionicform (e.g., protonated), or a non-ionizing trigger, which acts to effectconversion of the additve to its non-ionic form (e.g., deprotonated).

As the skilled person will know, there are several ways to protonate acompound in the presence of water. Likewise, there are several ways todeprotonate a compound in the presence of water. In accordance with someembodiments, a non-reversible switch between a non-ionic (e.g.,deprotonated amine) state and an ionic (protonated) state is sufficient.In accordance with other embodiments, a non-reversible switch between anionic (e.g., protonated amine) state and a non-ionic (deprotonated)state is sufficient. In preferred embodiments the switching betweenionic and non-ionic states is reversible. Accordingly the followingdiscussion will describe several triggers.

An example of a non-ionizing trigger for converting the ionic state(e.g., protonated amine) to the non-ionic state (e.g., deprotonatedamine) in an aqueous solution that has little or no dissolved CO₂, isaddition of a base to the aqueous solution. An example of an ionizingtrigger for converting the non-ionic state (e.g., deprotonated amine) tothe ionic state (e.g., protonated amine) in an aqueous solution, isaddition of an acid to the aqueous solution.

The compound of formula (1) can advantageously be converted, in thepresence of water, from a water-soluble non-ionic amine form to an ionicform that is also water-soluble. The conversion occurs when the aqueousnon-ionic solution is contacted with an ionizing trigger that is a gasthat liberates hydrogen ions in the presence of water. Hydrogen ionsprotonate the amine nitrogen of the non-ionic compound to form a cationand, in the case of a CO₂ trigger, bicarbonate anion acts as acounterion and a salt form is formed. This aqueous salt solution is asingle-phase ionic aqueous solution. More particularly, the ionic formis an ammonium salt. One skilled in the art will recognize that a smallamount of carbonate anions will also form and may act as counterions tothe protonated ammonium cations.

In the example in which the additive is immiscible or insoluble, orpoorly miscible or poorly soluble, in water, it can be converted, in thepresence of water, to an ionic form that is more water-soluble. Forexample the conversion can occur when the mixture of non-ionic additiveand water is contacted with a trigger gas that liberates hydrogen ionsin the presence of water. Hydrogen ions protonate the amine nitrogen ofthe non-ionic compound to form a cation and, in the case of a CO₂trigger, bicarbonate anion acts as a counterion and a salt form isformed. This aqueous salt solution is a single-phase ionic aqueoussolution. More particularly, the ionic form is an ammonium salt. Oneskilled in the art will recognize that a small amount of carbonateanions will also form and may act as counterions to the protonatedammonium cations.

As used herein, “gases that liberate hydrogen ions” fall into twogroups. Group (i) includes gases that liberate hydrogen ions in thepresence of a base, for example, HCN and HCl (water may be present, butis not required). Group (ii) includes gases that when dissolved in waterreact with water to liberate hydrogen ions, for example, CO₂, NO₂, SO₂,SO₃, CS₂ and COS. For example, CO₂ in water will produce HCO₃ ⁻(bicarbonate ion) and CO₃ ²⁻ (carbonate ion) and hydrogen counterions,with bicarbonate rather than carbonate being the predominant anionicspecies at pH 7. One skilled in the art will recognize that the gases ofgroup (ii) will liberate a smaller amount of hydrogen ions in water inthe absence of a base, and will liberate a larger amount of hydrogenions in water in the presence of a base.

Preferred gases that liberate hydrogen ions are those wherein the saltform switches to its non-ionic (amine) form when the same gas isexpelled from the environment. CO₂ is particularly preferred. Hydrogenions produced from dissolving CO₂ in water protonate the amine. In suchsolution, the counterion for the ammonium ion is predominantlybicarbonate. However, some carbonate ions may also be present insolution and the possibility that, for example, two ammonium molecules,each with a single positive charge, associate with a carbonatecounterion is not excluded. When CO₂ is expelled from the solution, theammonium cation is deprotonated and thus is converted to its non-ionic(amine) form.

Of group (ii) gases that liberate hydrogen ions, CS₂ and COS behavesimilarly to CO₂ such that their reaction with amine and water is fairlyeasily reversed. However, they are not typically preferred because theiruse in conjunction with water and an amine could cause the formation ofhighly toxic H₂S. In some embodiments of the invention, alternativegases that liberate hydrogen ions are used instead of CO₂, or incombination with CO₂, or in combination with each other. Alternativegases that liberate hydrogen ions (e.g., HCl, SO₂, HCN) are typicallyless preferred because of the added costs of supplying them andrecapturing them, if recapturing is appropriate. However, in someapplications one or more such alternative gases may be readily availableand therefore add little to no extra cost. Many such gases, or the acidsgenerated from their interaction with water, are likely to be so acidicthat the reverse reaction, i.e., converting the ammonium salt to theamine form, may not proceed to completion as easily as the correspondingreaction with CO₂. Group (i) gases HCN and HCl are less preferredtriggers because of their toxicity and because reversibility wouldlikely require a strong base.

Contacting a water-soluble compound of formula (1) with a CO₂, CS₂ orCOS trigger in the presence of water may preferably comprise: preparinga switchable water comprising water and a water-soluble additive offormula (1); and contacting the switchable water with a CO₂, CS₂ or COStrigger. Alternatively, the contacting a water-soluble compound offormula (1) with CO₂, CS₂ or COS in the presence of water may comprise:first preparing an aqueous solution of CO₂, CS₂ or COS in water; andsubsequently mixing the aqueous solution with a water-soluble additiveof formula (1) to form a switchable water. Alternatively, contacting awater-soluble additive of formula (1) with CO₂, CS₂ or COS in thepresence of water may comprise: dissolving CO₂, CS₂ or COS in awater-soluble additive of formula (1) that is in a liquid state toprovide a liquid; and mixing the non-aqueous liquid with water to form aswitchable water.

Contacting a water-insoluble compound of formula (1) with a CO₂, CS₂ orCOS trigger in the presence of water may preferably comprise: preparinga switchable water comprising water and a water-insoluble additive offormula (1); and contacting the switchable water with a CO₂, CS₂ or COStrigger. Alternatively, the contacting a water-insoluble compound offormula (1) with CO₂, CS₂ or COS in the presence of water may comprise:first preparing an aqueous solution of CO₂, CS₂ or COS in water; andsubsequently mixing the aqueous solution with a water-insoluble additiveof formula (1) to form a switchable water. Alternatively, the contactinga water-insoluble additive of formula (1) with CO₂, CS₂ or COS in thepresence of water may comprise: dissolving CO₂, CS₂ or COS in awater-insoluble additive of formula (1) that is in a liquid state toprovide a liquid; and mixing the non-aqueous liquid with water to form aswitchable water.

Depletion of CO₂, CS₂ or COS from a switchable water is obtained byusing a non-ionizing trigger such as: heating the switchable water;exposing the switchable water to air; exposing the switchable water tovacuum or partial vacuum; agitating the switchable water; exposing theswitchable water to a gas or gases that has insufficient CO₂, CS₂ or COScontent to convert the non-ionic state to the ionic state; flushing theswitchable water with a gas or gases that has insufficient CO₂, CS₂ orCOS content to convert the non-ionic state to the ionic state; or anycombination thereof. A gas that liberates hydrogen ions may be expelledfrom a solution by simple heating or by passively contacting with anonreactive gas (“flushing gas”) or with vacuum, in the presence orabsence of heating. Alternatively and conveniently, a flushing gas maybe employed by bubbling it through the solution to actively expel a gasthat liberates hydrogen ions from a solution. This shifts theequilibrium from the ionic ammonium form to non-ionic amine. In certainsituations, especially if speed is desired, both a flushing gas and heatcan be employed in combination as a non-ionizing trigger.

Preferred flushing gases are N₂, air, air that has had its CO₂ componentsubstantially removed, and argon. Less preferred flushing gases arethose gases that are costly to supply and/or to recapture, whereappropriate. However, in some applications one or more flushing gasesmay be readily available and therefore add little to no extra cost. Incertain cases, flushing gases are less preferred because of theirtoxicity, e.g., carbon monoxide. Air is a particularly preferred choiceas a flushing gas, where the CO₂ level of the air (today commonly 380ppm) is sufficiently low that an ionic form (ammonium salt) is notmaintained in its salt form. Untreated air is preferred because it isboth inexpensive and environmentally sound. In some situations, however,it may be desirable to employ air that has had its CO₂ componentsubstantially removed as a nonreactive (flushing) gas. By reducing theamount of CO₂ in the flushing gas, potentially less salt or amine may beemployed. Alternatively, some environments may have air with a high CO₂content, and such flushing gas would not achieve sufficient switching ofionic form to non-ionic amine form. Thus, it may be desirable to treatsuch air to remove enough of its CO₂ for use as a trigger.

CO₂ may be provided from any convenient source, for example, a vessel ofcompressed CO₂(g) or as a product of a non-interfering chemicalreaction. The amines of the invention are able to react with CO₂ at 1bar or less to trigger the switch to their ionic form.

It will be understood by the skilled person in the art that regenerationof a water-miscible compound of formula (1) from an ionic aqueoussolution of a salt of formula (2) can be achieved by either active orpassive means. The regeneration may be achieved passively if aninsufficient concentration of an ionizing trigger, such as CO₂, ispresent in the surrounding environment to keep the additive switched tothe ionic form. In this case, an ionizing trigger such as CO₂ could begradually lost from the aqueous solution by natural release. Nonon-ionizing trigger, such as heating or active contacting with flushinggases would be required. Heating or contacting with flushing gases wouldbe quicker but may be more expensive.

In studies described herein (see example 7), efficient contact betweengas and solution was obtained using a fritted glass apparatus. Heat canbe supplied from an external heat source, preheated nonreactive gas,exothermic dissolution of gas in the aqueous ionic solution, or anexothermic process or reaction occurring inside the liquid. In initialstudies, the non-ionizing trigger used to expel CO₂ from solution and toswitch from ionic form to amine was heat. However, CO₂ was expelled, andthe salt was converted to the amine by contacting with a flushing gas,specifically, nitrogen. It is also expected that CO₂ can be expelledfrom the ionic solution merely by passively exposing the solution toair.

In some embodiments the amine additive in its non-ionic state is aliquid, in other embodiments the amine additive in its non-ionic stateis a solid. Whether liquid or solid, they may be miscible or immisciblewith water.

In some embodiments the ionic form of the additive (e.g., ammoniumbicarbonate) is a liquid, in other embodiments the ionic form of theadditive is a solid. Whether liquid or solid, they may be miscible orimmiscible with water.

It is not significant whether neat ammonium bicarbonate salt is a solidor a liquid as long as it is water soluble such that a single phasesolution is provided of the ionic aqueous solution. It will be apparentthat at least a molar equivalent of water is required to react with theCO₂ to provide the carbonic acid to protonate a nitrogen site(s) of theamine group of the compound of formula (1) to form the ammonium cation.

In embodiments where a neat ammonium bicarbonate of formula (3) is asolid and not a liquid, more than a molar equivalent of water relativeto the number of nitrogen sites should be present in the aqueoussolution to ensure the complete dissolution of the salt in the ionicaqueous solution. In some embodiments, the amount of water is 1 or moreweight equivalents relative to the compound of formula (1).

In some embodiments, the mole ratio of water and basic nitrogen sites inthe amine capable of protonation is at least about equimolar. It will beapparent to one skilled in the art that when the ionic form is preparedfrom this mixture, there will remain little or no unreacted reactant(s),and thus little or no water after conversion to the salt form.

In other embodiments, the ratio of non-gaseous reactants is greater thanequimolar, i.e., the number of moles of water is greater than the numberof moles of basic nitrogen sites in the amine capable of protonation.This provides additional, unreacted water which is not consumed in theswitching reaction. This may be necessary to ensure a single phaseliquid mixture should the neat resulting salt be a solid, therebyproviding a single phase aqueous solution. In some embodiments, a veryhigh ratio of moles of water to moles of non-ionic additive (amine) ispreferred so that the cost of the aqueous solvent can be decreased; itis assumed that the amine additive is more expensive than the water. Itis preferred that sufficient water is present to dissolve the saltformed after switching so that an ionic aqueous solution is obtained.

If insufficient water is present to solubilize a solid ammoniumbicarbonate formed after switching, unsolubilized salt will be presentas a precipitate. For instance, should the ratio of {moles of water} to{moles of basic nitrogen sites in the amine capable of protonation} beequimolar, substantially all the water would be consumed in a completeswitching reaction. If the salt was a solid rather than an ionic liquid,this solid would form as a precipitate. The formation of the salt as aprecipitate may be advantageous in some circumstances because it iseasily recoverable, for instance by filtration.

Systems and Methods Employing Switchable Water

As described briefly above, an aspect provided herein is a method andsystem for switching the ionic strength of water or an aqueous solution.The method comprises the step of mixing water or an aqueous solutionwith a switchable additive, before, after or simultaneously with theintroduction of an ionizing trigger to ionize the switchable additiveand consequently raise the ionic strength of the mixture of the water orthe aqueous solution and the switchable additive. Optionally, the methodadditionally comprises the step of introducing a non-ionizing trigger toreverse the ionization of the switchable additive.

Also provided is a switchable water system that comprises: means forproviding a switchable additive comprising at least one nitrogen that issufficiently basic to be protonated by carbonic acid; means for addingthe additive to water or to an aqueous solution to form an aqueousmixture with switchable ionic strength; means for exposing the water oraqueous solution to an ionizing trigger, such as CO₂, COS, CS₂ or acombination thereof, to raise the ionic strength of the aqueous mixturewith switchable ionic strength; and, optionally, means for exposing themixture with raised ionic strength to a non-ionizing trigger, such as(i) heat, (ii) a flushing gas, (iii) a vacuum or partial vacuum, (iv)agitation, (v) or any combination thereof, to reform the aqueous mixturewith switchable ionic strength. As will be appreciated, the means forexposing the water or aqueous solution to the ionizing trigger, can beemployed before, after or together with the means for adding theadditive to the water or the aqueous solution.

FIG. 21 provides an example of a switchable water system as describedabove. In the system embodiment depicted in FIG. 21, the system includesmeans for contacting the non-ionized form of a switchable water with theionizing trigger, which, in this example is CO₂. Following contact withthe ionizing trigger, the switchable water is reversibly converted toits ionic form. As also depicted in FIG. 21, the system in this examplefurther comprises a means for introducing a non-ionizing trigger to theionized form of the switchable water. In this example, the non-ionizingtrigger is air.

The following is a non-limiting list of applications of systems andmethods employing switchable water:

-   -   1. In Osmosis (either by Forward Osmosis (FO) or by Forward        Osmosis followed by Reverse Osmosis (FO/RO))        -   a. For production of freshwater by desalination of seawater            or brackish water.        -   b. For partial dewatering of wastewater, process water, or            other industrial aqueous solutions (whether waste or in a            process). The osmosis concentrates the wastewater/process            water/industrial aqueous solution and produces a purified            water stream that can be directly recycled or disposed of,            or further purified or processed for recycling or disposal.    -   2. In Forcing Immiscibility        -   a. For the drying of (i.e., removal of water from) organic            liquids by forcing the water-content in the organic liquid            to form a second liquid phase.        -   b. For the recovery of organic liquids from water by forcing            the organic content in the water to form a second liquid            phase.        -   c. For forcing two immiscible aqueous phases to form (for            separating water-soluble polymers such as polyethylene            glycol (PEG) from salts or for concentrating solutions of            water-soluble polymers such as PEG).    -   3. In Forcing Insolubility        -   a. For recovering a solid compound or compounds (such as an            organic product, e.g., an active pharmaceutical ingredient            (API) or a contaminant) from water or from an aqueous            mixture. The recovered solid compound or compounds can be            the target compound or compounds or an undesired compound or            compounds (such as contaminants or by-products). This can be            useful, for example, after an organic synthesis in water;            after the extraction of an organic into water; for            recovering proteins from water; for decontaminating            contaminated water; for causing a coating, dye or mordant to            come out of aqueous solution and attach itself onto a solid.        -   b. For adjusting the solubility of salts in water (i.e., the            solubility of the salt would be different in the ionic            switchable water than in the non-ionic switchable water).            Possibly useful in mining or in separations involving salts.        -   c. For adjusting the partition coefficient of solutes            between an aqueous phase and an organic liquid phase.            Certain systems and methods employing switchable water are            useful in catalysis, extractions, washing of products,            separations of mixtures, etc.    -   4. In Breaking Dispersions        -   a. For breaking emulsions. Can be useful, for example, in            the oil industry during or after enhanced oil recovery,            during or after pipelining of heavy crudes or bitumen,            during or after wastewater treatment, in the treatment of            rag layers.        -   b. For breaking suspensions. Can be useful, for example, in            removal of suspended solids/particles from water (e.g.,            wastewater or storm water). For example, the present methods            and systems can be used in oil sands processing and tailings            ponds, in mining, in the treatment of wastewater from            mining, in minerals processing and separation, in treatment            of wastewater from other industries, in latex preparation,            handling and precipitation, in            emulsion/microemulsion/miniemulsion/suspension            polymerization. In a specific example, the methods and            systems can be used in removal of fine clay particles from            water.        -   c. For breaking foams and froths. Can be useful, for            example, in the oil industry for suppressing foams, in            mineral separations, in the treatment of aqueous streams            after mineral separations.    -   5. In Causing Other Properties of Aqueous Solutions to Change        -   a. For modifying density. The density of the ionic form of a            switchable water is expected to be different from the            density of the non-ionic version. This density change can be            useful in the separation of solid materials like polymers            because some would float and some would sink at each density            and modifying the density could allow the separation of            different polymers at different densities.        -   b. For modifying conductivity, for example, in sensors,            liquid switches.        -   c. For modifying viscosity. The viscosity of the ionic form            of a switchable water solution is different from the            non-ionic version.

In specific embodiments, this system and method are used, for example:

-   -   to remove water from a hydrophobic liquid or a solvent;    -   to remove water from a hydrophilic organic liquid such as an        alcohol;    -   to remove or isolate a solute from an aqueous solution;    -   to remove or isolate a hydrophobic liquid or solvent from an        aqueous mixture;    -   to remove salt and/or generate fresh water in a desalination        process;    -   to destabilize or disrupt micelles and/or to deactivate a        surfactant;    -   to provide a switchable antifreeze, a switchable electrolyte        solution, a switchable conducting solution, or an electrical        switch; or    -   to provide a CO₂, COS, CS₂ sensor.

In one embodiment, there is provided a method of extracting a selectedsubstance from a starting material(s) that comprises the selectedsubstance. In some embodiments, the selected substance is soluble in anaqueous solution comprising the non-ionic form of a swichable water(comprising the a non-ionic form of the switchable additive) with zeroor low ionic strength, and the selected substance is insoluble in anaqueous solution comprising the ionic form of a switchable water(comprising the ionized form of the additive), which has a higher ionicstrength. For instance, the starting material may be a solid impregnatedwith the selected substance. For another instance, the starting materialmay be a liquid mixture of the selected substance and a hydrophobicliquid. This method of extracting a selected substance is particularlyeffective if the selected substance is soluble in the non-ionic aqueoussolution. The selected substance, which may be a liquid or a solid,dissolves in the non-ionic aqueous solution comprising an additive offormula (1) and can thereby be readily separable from anywater-insoluble remaining starting material (e.g., by filtration) andcan be separated from the hydrophobic liquid (e.g., by decantation).Once the non-ionic aqueous solution comprising the selected compound isisolated, the selected substance can be separated from the aqueous phase(i.e., “salted out”) by converting the non-ionic aqueous solution to anionic aqueous solution. The selected substance will then separate outand can be isolated.

Using methods and systems described herein it is possible to separatecertain water-soluble selected compounds from an aqueous solution. Oncethe selected compounds are dissolved in an aqueous solution, andoptionally separated from other non-soluble compounds by, for example,filtration, the selected compounds can be isolated from the aqueoussolution without having to input a large amount of energy to boil offthe water. Conveniently, this separation is done by increasing the ionicstrength (amount of charged species) in the aqueous solution (morecommonly referred to as “salting out”) resulting in a separation of theselected compound from the distinct aqueous phase. The selected compoundcan then be isolated from the aqueous solution be decanting it orfiltering it, as appropriate. Thus, an aqueous solution whose ionicstrength is altered upon contact with a suitable trigger can dissolve orseparate from a selected compound in a controlled manner. Importantly,this method of salting out is readily reversible, unlike theconventional method of salting out (e.g., adding NaCl to water). Asystem for employing such a method includes, in addition to thecomponents set out above, means for mechanical separation of solids froma liquid mixture.

In an embodiment, the invention provides a method of removing water(i.e., drying) from hydrophobic liquids such as solvents. As describedin detail herein, additives form a salt in the presence of water andCO₂, COS or CS₂. Accordingly, additives added to wet solvent and anionizing trigger gas (in any combination) cause any water that was inthe wet solvent to separate out as a distinct ionic component in anaqueous phase. A system for employing such a method includes, inaddition to the components set out above, means for extracting a waterimmiscible liquid phase from an aqueous solution.

A conceptual model of such a system is shown in FIG. 1, which shows thereversible separation of tetrahydrofuran (THF) from an aqueous solutionof a compound of formula (1). This figure shows that when THF is mixedwith a non-ionic aqueous solution, THF is miscible with the non-ionicaqueous solution, providing a single phase. As discussed in workingexamples 1 and 2, THF was experimentally shown to be miscible with thenon-ionic aqueous solution. Further, THF was isolated from the mixtureby switching the additive in the solvent from its non-ionic form to itsionic form (ammonium bicarbonate) in order to increase the ionicstrength and force THF from the aqueous solution.

Specifically, as discussed in working examples 1 and 2, the aqueoussolution was contacted with CO₂ to switch the amine to its ammoniumbicarbonate form (ionic form) as shown by formula (3). The contactingwas carried out by treating a miscible mixture of THF, water andwater-soluble amine compound of formula (1) with carbonated water oractively exposing the mixture to CO₂. The THF then formed a non-aqueouslayer and the ammonium bicarbonate remained in an increased ionicstrength aqueous layer (“water+salt (3)”). The non-aqueous and aqueouslayers are immiscible and formed two distinct phases, which can then beseparated by decantation, for example. Once separated, the non-aqueousand aqueous layers provide an isolated non-aqueous phase comprising THFand an isolated aqueous phase comprising the ammonium bicarbonate formof additive in the switchable solvent. In this way, the solvent isseparated from the THF without distillation. While it is unlikely thatevery single molecule of THF will be forced out of the aqueous phase, amajority of the THF can be forced out by this method. The amount of THFthat remains in the aqueous phase will depend on several factors,including nature and concentration of additive, temperature, effect ofother species in solution, amount of CO₂ (or other gas(ses) thatreleases protons in water) in the water, and the number of basic siteson the additive that are protonable by carbonic acid.

The ammonium bicarbonate salt of formula (3) in the aqueous phase wasswitched back to its non-ionic form. The aqueous solution of salt (3)which has been switched back to a non-ionic aqueous solution can then beused to dissolve or extract further THF.

Note that the ability of the liquid mixture of water and amine additive(e.g., compound of formula (1)) to dissolve a selected compound may begreater than the ability of pure water to dissolve the same selectedcompound because the additive may help the desired compound to dissolvein the aqueous solution. This may be because of a polarity-loweringeffect of the amine, because of preferential solvation of the moleculesof the desired compound by the molecules of the amine additive, and/orbecause of a miscibility-bridging effect in which the addition of acompound of intermediate polarity increases the mutual miscibilitybetween a low-polarity liquid and a high-polarity liquid.

When the aqueous solutions with switchable ionic strength are switchedbetween their lower ionic strength state and their higher ionic strengthstate, characteristic of the solution are changed. Such characteristicsinclude: conductivity, melting point, boiling point, ability tosolubilise certain solutes, ability to solubilise gases, osmoticpressure, and there may also be a change in vapour pressure. Asdiscussed herein, the switchable ionic strength also affects surfactantsby changing their critical micelle concentration and by affecting theirability to stabilize dispersions. Variation of such characteristics canbe used, for example, the reversibly switchable ionic strength solutioncan be a reversibly switchable antifreeze, a reversibly switchableelectrolyte solution, or a reversibly switchable conducting solution.

A further aspect provides a non-ionic switchable water mixture that islargely nonconductive (or only weakly conductive) of electricity, thatbecomes more conductive when it is converted to its ionic form, and thatthis change is reversible. Such a conductivity difference would enablethe mixture to serve as an electrical switch, as a switchable medium, asa detector of CO₂, COS or CS₂, or as a sensor of the presence of CO₂,COS or CS₂. This ability of the ionic liquid to conduct electricity canhave applications in electrochemistry, in liquid switches and in sensorsand/or detectors. Common, affordable CO₂ sensors are typically effectiveat 2-5% CO₂. CO₂ sensors that work between 2-100% are usually large andprohibitively expensive. A chemical approach based on switchable ionicstrength solutions can cost much less.

Further provided is a method for maintaining or disrupting miscibilityof two liquids where the first liquid is miscible with low ionicstrength water but is immiscible with higher ionic strength water andthe second liquid is the reversible switchable ionic strength aqueoussolvent described herein. In a mixture of the first and second liquids,they are miscible when the switchable solvent is in its non-ionic form.To disrupt the miscibility, a trigger is applied, causing the ionicstrength of the switchable solvent to increase and the newly-immiscibleliquids to separate. Alternatively, the first liquid may be a liquidthat is miscible with aqueous solutions of high ionic strength andimmiscible with aqueous solutions of low ionic strength. In such a casethe ionic and non-ionic forms of the switchable solvent should be usedto maintain and disrupt the miscibility, respectively.

Another aspect is a method for “salting-in” of solutes that are moresoluble in water of high ionic strength than in water of low ionicstrength. For example, an aqueous solution of switchable additive athigh ionic strength is used as a solvent for a solute, and the switchingof the solution to low ionic strength causes the solute to form a secondphase or precipitate or to partition into an existing second phase.

Another aspect provides a method of deactivating surfactants.Surfactants (also known as detergents and soap) stabilize the interfacebetween hydrophobic and hydrophilic components. In aqueous solutions,detergents act to clean oily surfaces and clothing by making the(hydrophobic) oil more soluble in water (hydrophilic) by its action atthe oil-water interface. Once a cleaning job is finished, soapy waterwith hydrophobic contaminants remains. To recover the oil from the soapywater, salt can be added to the water and most of the oil will separatefrom the salt water. With the switchable ionic strength aqueous solutionof the present invention, after a cleaning job, the oil can be recoveredfrom the soapy water solution merely by applying a trigger to reversiblyincrease the solutions ionic strength. The trigger causes the ionicstrength to increase, thereby deactivating the surfactant. Manysurfactants are unable to function properly (effectively stabilizedispersions) at conditions of high ionic strength. The oil thenseparates from the aqueous phase, and can be decanted off. Then theaqueous solution can be triggered to decrease the ionic strength.Regenerated soapy water can then be reused, over and over.

Another aspect provides switchable water of switchable ionic strengthsthat are used to stabilize and destabilize emulsions, which may includesurfactant-stabilized emulsions. Emulsions of oil and water that includesurfactants are used in oil industries to control viscosity and enabletransport of oil (as an emulsion) by pipeline. Once the emulsion hasbeen transported, however, it is desirable to separate thesurfactant-supported emulsion and recover oil that is substantiallywater-free. In its non-ionized form, amine additive does notsignificantly interfere in the stability of an emulsion of water and awater-immiscible liquid (e.g., hexane, crude oil). However, onceswitched to its ionic form, the increased ionic strength of the solutioninterferes with the stability of the emulsion, resulting in a breakingof the emulsion. In surfactant-stabilized emulsions, the higher ionicstrength solution may interfere with the surfactant's ability tostabilize the emulsion. This reversible switch from lower to higherionic strength is preferable over destabilizing emulsions by traditionalmeans (i.e., increasing the ionic strength by adding of a traditionalsalt such as NaCl). This preference is because the increase in ionicstrength caused by the addition of a traditional salt is difficult toreverse without a large input of energy.

Creating an emulsion is possible, for example by adding awater-immiscible liquid to the lower ionic strength switchable aqueoussolution as described previously, to form two phases. Then, a surfactantthat is soluble in the aqueous phase should be added to a concentrationabove the critical micelle concentration of the surfactant. Shear ormixing of the mixture then creates an emulsion. As discussed above, theresultant emulsion can be destabilized by treatment with an ionizingtrigger, such as by bubbling it with CO₂, COS or CS₂ to raise the ionicstrength of the aqueous phase. Subsequent removal of CO₂, COS or CS₂ bytreatment with a non-ionizing trigger, such as by bubbling the mixturewith a flushing gas and/or by heating it lowers the ionic strengthallowing the system to return to the initial conditions.

Non-limiting examples of emulsions include mixtures of water with: crudeoil; crude oil components (e.g., gasoline, kerosene, bitumen, tar,asphalt, coal-derived liquids); oil (including oil derived frompyrolysis of coal, bitumen, lignin, cellulose, plastic, rubber, tires,or garbage); vegetable oils; seed oils; nut oils; linseed oil; tung oil;castor oil; canola oil; sunflower oil; safflower oil; peanut oil; palmoil; coconut oil; rice bran oil; fish oils; animal oils; tallow; orsuet. Other non-limiting examples of emulsions include water withcolloidal particles, colloidal catalysts, colloidal pigments, clay,sand, minerals, soil, coal fines, ash, mica, latexes, paints,nanoparticles including metallic nanoparticles, nanotubes.

Another aspect provides aqueous solutions of switchable ionic strength,or switchable water, which are used to stabilize and destabilize reverseemulsions.

A suspension is a finely divided solid that is dispersed but notdissolved in a liquid. In an aspect of the invention, aqueous solutionsof switchable ionic strength are used to stabilize and destabilizesuspension of solids in water, which may include surfactant-stabilizedsuspensions. In its non-ionized form, amine additive does not interferein the stability of a suspension. However, once the additive is switchedto its ionic form, the increased ionic strength may significantlydestabilize a suspension and/or it may inhibit the ability of asurfactant to stabilize such a suspension, resulting in coagulation ofthe solid particles. This reversible switch from lower to higher ionicstrength is preferable to destabilizing a suspension by addingtraditional salts (e.g., NaCl) because the increase in ionic strengthcaused by the addition of a traditional salt is difficult to reversewithout a large input of energy. Typical examples of such suspensionsmay include polymers (e.g., polystyrene), clays, minerals, tailings,colloidal dyes, and nanoparticles including metallic nanoparticles.Increasing the ionic strength of the solution by applying a trigger,causes small solid particles to aggregate or coagulate to form largerparticles that settle to the bottom of the solution. Application of atrigger to convert from higher ionic strength to lower ionic strength(e.g., removal of CO₂) allows for redispersion of the particles,regenerating the suspension.

In an alternative aspect there is provided, aqueous solutions comprisingswitchable water of switchable ionic strength that are used to stabilizeand destabilize foam (i.e., gas-in-liquid), which may includesurfactant-stabilized foams. In its non-ionized form, the switchableadditive does not interfere in the stability of a foam. However, oncethe additive is switched to its ionic form, the increased ionic strengthinterferes with the stability of the foam and/or inhibits a surfactant'sability to stabilize a foam, resulting in the breaking of the foam. Thisreversible switch from lower to higher ionic strength is preferable todestabilizing foams by adding a traditional salt (e.g., NaCl) becausethe increase in ionic strength caused by the addition of a traditionalsalt is difficult to reverse without a large input of energy.

A gas in liquid emulsion can exist in the lower ionic strength aqueoussolution that includes an amine additive. When a trigger is applied toincrease the solution's ionic strength the foam is destabilized. Theapplication of a trigger to convert it from the higher ionic strengthsolution to the lower ionic strength solution leads a newly generatedfoam to be stabilized in the solution. In this situation, a non-ionizingtrigger to release CO₂, COS or CS₂ would preferably be application of aflushing gas (e.g., N₂, air). In an embodiment of the method ofseparating a solute from an aqueous solution, instead of separating thesolute in a neat form, it is possible to add a water immiscible liquid(e.g., n-octanol) to the mixture. In the lower ionic strength form, thesolute has a given partitioning between the aqueous phase and thehydrophobic phase. With application of a trigger, the aqueous phaseconverts to a higher ionic strength solution, which causes more of thesolute to partition into the hydrophobic phase. In this embodiment,rather than the solute forming its own phase, the solute is dissolved inthe hydrophobic phase. If desired, another trigger (e.g., removal ofCO₂) lowers the ionic strength allowing the solute to return to theaqueous phase. A system for employing such a method would include, inaddition to the components described above, means for providing thewater immiscible liquid and means for extracting a water immiscibleliquid phase from an aqueous solution

In another aspect there is provided, aqueous solutions of switchableionic strength that are used to create aqueous/aqueous biphasic systems.A lower ionic strength aqueous solution with amine additive and awater-soluble polymer (e.g., poly(ethylene glycol) exists as a singlephase. With application of a trigger, the aqueous phase converts to ahigher ionic strength solution, which causes the mixture to form twoseparate phases. Specifically, the phases are the polymer and water thatit carries with it since is quite water soluble and the aqueous solutionof higher ionic strength. If desired, another trigger (e.g., removal ofCO₂) lowers the ionic strength causing the system to recombine into asingle aqueous phase.

In an embodiment of this aspect, there are two solutes in the aqueoussolution of switchable ionic strength that comprises a water-solublepolymer (e.g., poly(ethylene glycol). The two solutes may be, forexample, two different proteins. Each protein will separate from higherionic strength aqueous solution (i.e., “salt out”) at a distinct andspecific ionic strength. If a trigger increases the ionic strength ofthe switchable solution such that only one of the two proteins separatesfrom the higher ionic strength aqueous phase, the one protein willpartition into the water and water-soluble-polymer layer so that it isseparated from the other protein. As described above, with anothertrigger to reduce the ionic strength, the aqueous solution can be usedover and over again. In another embodiment of this aspect, a solute maypartition from the higher ionic strength aqueous solution into the waterwith water-soluble-polymer layer in the form of a solid.

Another aspect of the invention is a method of drying hydrophobicliquids by separating the hydrophobic liquid from its water contaminant.As described herein, this separation is effected by adding an additivethat forms a salt in the presence of water and CO₂, COS or CS₂. The saltcan then be isolated from the hydrophobic liquid thereby removing itswater contaminant. Non-limiting examples of hydrophobic liquids includesolvents, alcohols, mineral oils, vegetable oils, fish oils, seed oils.In some embodiments of the invention the liquid that needs to besimilarly dried is a hydrophilic liquid such as a smaller alcohol.

Yet another aspect of the invention provides a method of reversiblylowering an aqueous solution's boiling point. Another aspect of theinvention provides a method of reversibly increasing an aqueoussolution's boiling point.

Another aspect of the invention provides a method and system foraltering the viscosity of an aqueous solution or mixture. It has beenfound that the use of switchable water to alter the ionic strength of anaqueous solution also results in an alteration in the viscosity of theaqueous solution. In one embodiment, the method and system for switchingthe viscosity of an aqueous system facilitates a reversible small changein viscosity. Such a method and system makes use of lower molecularweight switchable water additives. The dissolution in water of a lowermolecular weight switchable water additive, in its non-ionic form, willgenerate a modest increase in viscosity over water alone. However, ithas been found that addition of CO₂ to such a system still causes adecrease in viscosity making it valuable in those situations thatrequire only small changes in viscosity.

In another embodiment, the method and system for switching the viscosityof an aqueous solution facilitates a relatively large reversible changein viscosity. Such a method and system makes use of higher molecularweight switchable water additives. The dissolution in water of a highermolecular weight switchable water additive, in its non-ionic form, willgenerate a significant increase in viscosity over water alone. As willbe appreciated by a worker skilled in the art, the large molecularweight switchable water additive must be sufficiently soluble in water,when the additive is in its non-ionic form, to generate the largeincrease in viscosity over water alone. When a suitable ionizing triggeris introduced, the ionic form of the high molecular weight switchablewater additive is generated, leading to a relatively large decrease inthe viscosity of the solution.

A system and method for reversible alteration of viscosity would beuseful, for example, in point to point transport of an otherwise viscousmaterial in which its application calls for a higher viscosity, such asin conventional waterflooding techniques. Conventional waterfloodingtechniques are used for enhanced oil and gas recovery operations. Lowviscosity, ionic form, polymer solutions could be injected into oil andgas wells at pressures lower than conventional polymer additives, atwhich point the solutions could be switched to a higher viscosity by useof a suitable trigger, which may help promote oil flow towardscollection points. Once operations are complete it may be possible tolower the viscosity of the solution by switching on the polymer additiveto it's ionic form, at which point the ionic form of the polymeradditive solution could be pumped out of the well.

Another aspect of the invention provides a method and system forreversibly lowering an aqueous solution's boiling point. Another aspectof the invention provides a method of reversibly increasing an aqueoussolution's boiling point.

An aspect of the invention provides a reversibly switchable antifreeze.

An aspect of the invention provides a reversibly switchable electrolyte.

An aspect of the invention is a method for reversibly controlling theattractive and repulsive forces existing in a multiphase mixture such asoil sands (also known as tar sands or bituminous sands). For example, insome embodiments, the high ionic strength aqueous solution of switchableadditive could make some or all of the interactions between componentsbecome attractive, while some or all of the interactions would be lessattractive or even be repulsive in the presence of low-ionic strengthaqueous solution. Repulsive forces, for example between clay andbitumen, between clay particle and another clay particle, or betweenclay and sand particles, are acceptable or even desired in theseparation of oil sands into bitumen and tailings, while, in contrast,repulsive forces are acceptable or even desired in the treatment andsettling of tailings.

In preferred embodiments, conversion of the compound of formula (1) tothe salt is complete. In certain embodiments, the conversion to salt isnot complete; however, a sufficient amount of the amine is converted tothe salt form to change the ionic strength of the liquid. Analogously,in some embodiments, the conversion of ionic form back to the aminecompound of formula (1) that is water-miscible may not be complete;however a sufficient amount of the salt is converted to the aminecompound of formula (1) that is water-miscible to lower the ionicstrength of the solution.

An advantage of switchable water described herein is that it canfacilitate syntheses and separations by eliminating the need to removeand replace water or an aqueous solution after each reaction step. Withtriggers that are capable of causing a drastic change in the ionicstrength of the water or aqueous solution while it is still in thereaction vessel, it may be possible to use the same water or aqueoussolution for several consecutive reaction or separation steps. Thiswould eliminate the need to remove and replace the solvent water oraqueous solution. For example, a chemical reaction that requires anaqueous solvent could be performed using the switchable water while inits amine form as the solvent. Once the reaction is complete, thesolvent could be switched to its higher ionic strength form which issubstantially incapable of dissolving a product and/or side-product ofthe reaction. This would force the product to precipitate, if solid, orbecome immiscible, if liquid. The solvent could then be separated fromthe product by physical means such as, for example, filtration ordecantation. The solvent could then be switched back to its lower ionicstrength form by switching the ionic form to the water-miscible amineand reused. This method allows the use of an aqueous solvent without therequirement for an energy-intensive distillation step to remove thesolvent. Such distillation steps may be complex because both the solventand the product may have similar boiling points.

Reuse and recycling of solvents of the invention provide both economicand environmental benefits. The time required to switch between thehigher and lower ionic strength solvents is short as demonstrated bystudies described in Examples 6 and 7. In Example 6, an incompleteswitch between an additive in ionic form and nonionic form can occur in300 minutes with heating. Example 6 also shows that in excess of about90% of the ionic forms of MDEA and THEED were converted back to theirnon-ionic forms. THEED was 98% deprotonated after 120 minutes of heating(75° C.) and bubbling with N₂ using a single needle. As shown in FIG. 12and described in Example 7, conductivity of TMDAB was reducedapproximately 95% in 90 minutes when heated at 80° C. and N₂ was bubbledthrough a glass frit. This result demonstrated a dramatic ionic strengthreduction.

It is advantageous to convert from non-ionic amine form to ionic formand then back again (or vice-versa). The solvent comprising water andthe additive in its amine form could be miscible with another liquid,and then the solvent could be switched to increased ionic strength formto allow for separation of the resulting two liquid components. Theliquid components may or may not appear as distinct layers. Methods forseparation of the components may include decanting, or centrifugingfollowed by decanting. After separation, it is desirable to convert anionic form of the additive back to its non-ionic amine form in water.Thus the solvent can be reused.

In accordance with a specific embodiment, there is provided a system, asdepicted in FIG. 22, for isolating or purifying one or more compoundsfrom a mixture. The system includes a means, 10 (denoted in FIG. 22),for introducing a non-ionic switchable water to a mixture of compounds.In this example, the first compound is miscible in the non-ionic form ofswitchable water and the second compound is insoluble. Accordingly, thesystem additionally comprises means, 20 (denoted in FIG. 22), formechanically collecting the second compound that is insoluble in thenon-ionic switchable water. For example, the system can include meansfor collecting or removing the second compound by filtration therebyleaving a mixture, 30 (denoted in FIG. 22), that includes the non-ionicswitchable water and the first compound. The system depicted in FIG. 22further comprises means for contacting mixture, 30 (denoted in FIG. 22),with an ionizing trigger (e.g., CO₂) to increase the ionic strength ofthe switchable water and generate a two-phase mixture, 40 (denoted inFIG. 22), in which the first compound is no longer miscible with theswitchable water. The system shown in FIG. 22 additionally comprisesmeans, 50 (denoted in FIG. 22), for collecting the immiscible firstcompound. For example, the system can include means for decanting orotherwise collecting the top layer of mixture, 40 (denoted in FIG. 22),which top layer includes the first compound. Optionally, this systemfurther includes means for reversing the ionic strength increase of theswitchable water by introducing a non-ionizing trigger, such as air, toreform the non-ionic form of the switchable water, 60 (denoted in FIG.22).

Switchable water can also be useful in water/solvent separations inbiphasic chemical reactions. Separation of a liquid from a switchablesolvent can be effected by switching the switchable solvent to itshigher ionic strength form. This ability to separate solvents may beuseful in many industrial processes where, upon completion of areaction, the solvent can be switched to its higher ionic strength formwith the addition of a trigger allowing for facile separation of the twodistinct phases. Thus a switchable ionic strength solvent may be used inits lower ionic strength form as a medium for a chemical reaction. Uponcompletion of the reaction, the chemical product is readily separatedfrom solution by switching the solvent to its higher ionic strengthform. The switchable water solvent can then be recovered and reused.

To gain a better understanding of the invention described herein, thefollowing examples are set forth. It should be understood that theseexamples are for illustrative purposes only. Therefore, they should notlimit the scope of this invention in any way.

In the following Working Examples, a variety of tertiary amines havebeen studied for their properties as switchable additives in switchableionic strength aqueous solutions (i.e., switchable water).

Results presented in the working examples, figures and tables show thatsix tertiary amines, selected from monoamines, diamines, triamines,tetraamines exhibited reversible switching ionic strength behavior. Allof these compounds were miscible with water in aqueous solution, and inthe presence of CO₂ switched to ammonium bicarbonate salt forms whichwere soluble in the aqueous phase. In addition, the working examples,figures and tables show polyamines that were successfully used toreversibly switch ionic strength behavior of aqueous systems.

Variations to the structure of these amine compounds are well within theskill of the person of ordinary skill in the art pertaining to theinvention. These include minor substitutions, varying the length of ahydrocarbon chain, and the like.

As described in the working examples, several salts of formulae (2) and(3), and of polyamines have been formed according to the invention byreacting CO₂ with aqueous solutions of water-miscible amine compounds offormulae (1) and (4). The water system advantageously provides a rapidrate of reaction to form the ammonium bicarbonate compounds from thewater-miscible compounds of formulae (1) and (4), and allows thedissolution of the ammonium bicarbonate compounds should they be solidat the temperature of the separation.

WORKING EXAMPLES

The following chemicals were used as received: ethanolamine,2-(methylannino) ethanol, chloroform-d (99.8+ atom % d), D₂O (99.9+ atom% d), acetonitrile-d₃ (99.8+ atom % d), methanol-d₄ (99.8+ atom % d),1,4-dioxane (99+%), DMAE, MDEA, TMDAB, THEED, DMAPAP and HMTETA(Sigma-Aldrich of Oakville, Ontario, Canada, or TCI of Portland, Oreg.,USA); THF (99+%) and ethyl acetate (99.5+%) (Calcdon Laboratories,Ontario, Canada); hydrochloric acid (˜12 M, Fischer Scientific, Ottawa,Ontario, Canada); and DMSO-d₆ (99.9+ atom % d) Cambridge Isotope Labs,St Leonard, Canada).

Diethyl ether was purified using a double-column solvent purificationsystem (Innovative Technologies Incorporated, Newbury Port, USA).Compressed gasses were from Praxair (Mississauga, Ontario, Canada): 4.0grade CO₂ (99.99%), 5.0 grade Ar (99.999%), supercritical grade CO₂(99.999%, H₂O<0.5 ppm), nitrogen (99.998%, H₂O<3 ppm) and argon(99.998%, H₂O<5 ppm).

Unless otherwise specified, water used in studies described herein wasmunicipal tap water from Kingston, Ontario, Canada that was deionized byreverse osmosis and then piped through a MilliQ Synthesis A10 apparatus(Millipore SAS, Molsheim, France) for further purification.

DBU (Aldrich, Oakville, Ontario, Canada, 98% grade) was dried byrefluxing over CaH₂ and distilled under reduced pressure onto 4 Åmolecular sieves and then deoxygenated by repeated freeze/vacuum/thawcycles or by bubbling with CO₂ followed by filtration to remove anybicarbonate precipitate.

¹H NMR and ¹³C NMR spectra were collected at 300 K on a Bruker AV-400spectrometer at 400.3 and 100.7 MHz, respectively.

Comparative Example 1 Amidine and Water System

A bicyclic amidine DBU (1,8-diazabicyclo-[5.4.0]-undec-7-ene), havingthe following structure, was investigated as an additive to provideswitchable ionic strength aqueous solutions.

DBU in non-ionic amidine form was soluble in water to provide a singlephase aqueous solution. It was found to be capable of switching to awater-soluble amidinium bicarbonate salt form in the presence of waterand a CO₂ trigger.

Initial experiments with a solution of DBU in water confirmed thatcompounds THF and 1,4-dioxane were miscible with the aqueous solution ofDBU (non-ionic form) in the absence of CO₂, and were immiscible with theaqueous solution in the presence of CO₂ in which the amidine had beenswitched into its amidinium bicarbonate ionic form. However, it wasfound that it was not possible to liberate CO₂ from the ionic solutionwith moderate heating. The two-phase mixture of non-aqueous THF andaqueous amidinium bicarbonate that had been generated from exposure toCO₂ could not be converted to a single-phase aqueous solution of DBU(non-ionic form) and THF.

Specifically, a 1:1:1 (v/v/v) mixture of DBU, water and compound wasadded to a six dram vial containing a magnetic stirrer and fitted with arubber septa. To introduce gas to the solution, a single narrow gaugesteel needle was inserted and gas was bubbled through. A second narrowgauge steel needle was inserted to allow venting of the gaseous phase.

When the compound was THF, a single phase miscible liquid mixture wasobserved. After CO₂ was bubbled through the solution for 15 min, themixture separated into two phases, an aqueous phase comprising asolution of the amidinium bicarbonate salt of DBU and a non-aqueousphase comprising THF. Bubbling N₂ through the mixture for several hoursat 50° C. failed to cause the phases to recombine.

Similarly, a 1:1:1 (v/v/v) mixture of DBU, water and 1,4-dioxane wasobserved to be a single phase miscible liquid mixture. After CO₂ wasbubbled through the solution for 60 min, the mixture separated into twophases, an aqueous phase comprising a solution of the amidiniumbicarbonate salt of DBU and a non-aqueous phase comprising 1,4-dioxane.Bubbling N₂ through the mixture for several hours at 50° C. failed tocause the phases to recombine.

Thus, although an aqueous solution of the amidine DBU can be switchedfrom a lower ionic strength form to a higher ionic strength form inorder to force out THF or 1,4-dioxane from the solution, the switchingwas not found to be reversible at the given experimental conditions. Itis likely that with high energy input such as high temperatures,reversible switching would be possible.

Comparative Example 2 Primary and Secondary Amine and Water Systems

A primary amine, ethanolamine, and a secondary amine, 2-(methylamino)ethanol were investigated as additives to provide switchable ionicstrength aqueous solutions. Six dram vials comprising 3:3:1 (v/v/v)mixtures of H₂O, amine, and compound were prepared as described forcomparative example 1.

A 3:3:1 (v/v/v) mixture of H₂O, ethanolamine, and THF was observed to bea single phase solution. This solution separated into two phases afterCO₂ was bubbled through the liquid mixture for 30 minutes, with anaqueous phase and a non-aqueous phase comprising THF. However, the twoseparate phases did not recombine into one miscible layer even after N₂was bubbled through the liquid mixture for 90 minutes at 50° C.

A 3:3:1 (v/v/v) mixture of H₂O, ethanolamine, and DMSO was observed tobe a single phase solution. This solution did not separate into twophases after CO₂ was bubbled through the liquid mixture for 120 minutes,however turbidity was observed.

A 3:3:1 (v/v/v) mixture of H₂O, 2-(methylamino)ethanol, and THF wasobserved to be a single phase solution. This solution separated into twophases after CO₂ was bubbled through the liquid mixture for 10 minutes,with an aqueous phase and a non-aqueous phase comprising THF. However,the two separate phases did not recombine into one miscible layer evenN₂ was bubbled through the liquid mixture for 90 minutes at 50° C.

Thus, in preliminary studies, certain primary and secondary amineadditives did not exhibit reversible switchable of ionic strengthcharacter. Although they switched from lower ionic strength to higherionic strength, they were not successfully switched from higher to lowerionic strength forms using the low energy input conditions of bubblingN₂ through the liquid mixture for 90 minutes at 50° C. It is noted thathigher temperatures were not used due to the limitation posed by theboiling point of THF of 66° C. Bubbling N₂ at a higher temperature mayhave led to the reverse reaction; however, THF evaporation would havebeen a problem. Although not wishing to be bound by theory the inventorssuggest that this irreversibility may be as a result of carbamateformation arising from the reaction of available N—H groups in theprimary and secondary amines with CO₂. The removal of carbamate ions inwater to give non-ionic amines by heating and bubbling a nonreactive gascan be difficult.

Example 1 Reversible Solvent Switching in Tertiary Amine/Water Systems

Three tertiary amines, DMAE, MDEA and THEED were investigated asadditives for switchable ionic strength solutions. DMAE and MDEA aremonoamines, and THEED is a diamine.

Six dram vials containing a magnetic stirrer and fitted with a rubbersepta were prepared with 1:1:1 w/w/w solutions of water, THF, and anadditive of tertiary amine compound of formula (1). To introduce gas tothe solution, a single narrow gauge steel needle was inserted and gaswas bubbled through. A second narrow gauge steel needle was inserted toallow venting of the gaseous phase.

The solutions were tested for switchable ionic strength character bybubbling CO₂ through the mixtures. The time necessary to observeseparation of the THF from the aqueous solution of the ionic bicarbonatesalt was recorded and is shown in Table 1 below. It was determined thatit typically takes 30 min of bubbling with CO₂ to separate out THF fromthe aqueous phase.

TABLE 1 Duration of CO₂ bubbling required to separate THF from aqueousphase comprising additive, and duration of N₂ bubbling required torecombine THF and the aqueous phase Time of CO₂ bubbling to Time of N₂bubbling to get phase separation get phase recombination Additive at 25°C. RT (min) at 50° C. (min) DMAE ~30 ~90 MDEA ~30 ~30 THEED ~30 ~60

After separation of the THF into a distinct non-aqueous phase wasobserved, nitrogen was then bubbled through the two-phase solutions at atemperature of 50° C. in order to remove CO₂ from the aqueous phase andswitch at least a portion of the ionic bicarbonate salt form back to thenon-ionic tertiary amine form. If the switching reaction wassufficiently reversible to reduce the ionic strength of the aqueousphase to a level allowing miscibility with the THF, conversion of thetwo-phase mixture to a single aqueous phase was observed.

As shown in Table 1, all of the tested tertiary amine additives could beswitched back from their ionic forms allowing recombination of the twophase mixtures to a single phase.

Example 2 Quantitative Determination of the Separation of Compound andAdditive Upon Switching

The three switchable aqueous solution systems of Example 1 were furtherinvestigated by ¹H NMR spectroscopy to quantify the amount of THFseparated from the aqueous phase upon switching of the additive to itshigher ionic strength ammonium bicarbonate form, and to quantify theamount of additive retained in the aqueous solution after switching.

To measure the extent of THF being forced out of an aqueous phase by anincrease in ionic strength, and the amounts of amine which remained inthe aqueous phase, 1:1:1 w/w/w solutions of water, THF, and amineadditive were prepared in graduated cylinders and the cylinders werecapped with rubber septa. After 30 minutes of bubbling CO₂ through theliquid phase at a flow rate of 3-5 mL min¹) as measured by a J&WScientific ADM 2000 Intelligent Flow Meter, from a single narrow gaugesteel needle, a visible phase separation was observed. The volumes ofeach phase were recorded. Aliquots of the non-aqueous and aqueous layerswere taken and dissolved in d₃-acetonitrile in NMR tubes. A known amountof ethyl acetate was added to each NMR tube as an internal standard.

¹H NMR spectra were acquired on a Bruker AV-400 NMR spectrometer at400.3 MHz for several replicate solutions of each mixture, and throughintegration of the ethyl acetate standard, a concentration of THF oradditive was calculated and scaled up to reflect the total volume of theaqueous or non-aqueous phase giving a percentage of the compound beingforced out or retained. The results are shown in Table 2 below.

TABLE 2 Amount of THF separated out of aqueous phase comprising additiveand amount of additive retained in the aqueous phase Amount of THFseparated Amount of additive retained Additive (mol %) (mol %) DMAE 76 ±1.7% 73.5 ± 2.0% MDEA 74 ± 3.0% 90.7 ± 1.5% THEED 67 ± 5.0% 98.6 ± 0.2%

The choice of tertiary amine additive was found to determine the amountof THF separated from the aqueous phase upon switching with CO₂ as shownin Table 2. When the tertiary amine was MDEA, 74 mol % of the THF wasseparated from the aqueous phase after bubbling CO₂ through thesolution, while 90.7 mol % of the additive (in ionic form) was retainedin the aqueous phase.

In some embodiments, it is preferred that substantially all of theadditive remains in the aqueous phase, rather than going into thenon-aqueous phase. This is because the utility of such solutions asreusable solvent systems would be increased if losses of the additivefrom the aqueous phase could be minimised. In the case of MDEA, 90.7 mol% of the MDEA remained in the aqueous phase. Thus, 9.3 mol % of the MDEAwas transferred into the non-aqueous phase comprising THF.Interestingly, THEED had the best retention in the aqueous phase atapproximately 98.6 mol %, even though it was least successful in forcingabout 67.7 mol % of the THF out of solution.

Subsequent bubbling of N₂ through the mixture lowered the ionic strengthand allowed the THF and aqueous phases to become miscible and recombine.At 50° C., this took about 30 minutes for the MDEA/THF/water mixture(Table 1). The rate of recombination would increase at highertemperatures, but this was not attempted in this case because of the lowboiling point of THF (boiling point 66° C.).

These experiments were also conducted using air rather than nitrogen asthe nonreactive gas to drive off CO₂ from the aqueous solution andswitch at least a portion of the additive from ionic form to non-ionicform. The time taken for the recombination of the aqueous andnon-aqueous phases was approximately the same for air as it was for N₂for each additive.

Example 3 Quantitative Determination of the Separation of Compound andAdditive Upon Switching at Different Additive Loadings

Reversible solvent switching in amine/water systems were explored fordifferent loadings of five additives, while keeping the ratio ofTHF:water at a constant 1:1 w/w. The additives were all tertiary aminesselected from monoamines DMAE and MDEA, diamine TMDAB, triamine DMAPAPand tetramine HMTETA.

To measure the extent of THF being forced out of an aqueous phase by anincrease in ionic strength, and the amounts of amine which remained inthe aqueous phase, 1:1 w/w solutions of water:THF were prepared ingraduated cylinders and the appropriate amount of amine additive added.The graduated cylinders were capped with rubber septa. This comparisoninvolved bubbling CO₂ through a single narrow gauge steel needle for 30min at a rate of 3-5 mL min⁻¹ as measured by a J&W Scientific ADM 2000Intelligent Flow Meter to switch the tertiary amine in aqueous solutionwith THF to ionic form. A second narrow gauge steel tube was provided tovent the gaseous phase. A visible phase separation into two liquidphases occurred, resulting in a non-aqueous and an aqueous phase.Aliquots of the non-aqueous and aqueous layers were taken and werespiked with a known amount of ethyl acetate to act as an internalstandard and the amounts of THF and additive were quantified by ¹H NMRintegration as discussed in Example 2. The results are shown in Table 3below.

TABLE 3 Comparison of relative amounts of amine additive to theseparation of THF from 1:1 w/w solutions of THF and H₂O and retention ofamine in aqueous phase when reacted with CO₂. THF:H₂O:Additive % THF %Additive Additive (w/w/w) Separated^([a]) Retained^([a]) DMAE 1:1:1 76 ±1.7% 73.5 ± 2.0% DMAE 3:3:1 85 ± 2.2% 93.9 ± 2.1% DMAE 5:5:1 74 ± 5.6%91.7 ± 2.6% DMAE 10:10:1 75 ± 0.3% 98.3 ± 0.4% MDEA 1:1:1 74 ± 3.0% 90.7± 1.7% MDEA 3:3:1 74 ± 3.8% 95.7 ± 1.5% MDEA 5:5:1 72 ± 0.3% 95.2 ± 1.5%MDEA 10:10:1 66 ± 3.0% 96.6 ± 0.6% TMDAB 3:3:1 87 ± 1.3% 87.1 ± 2.1%TMDAB 5:5:1 87 ± 0.6% 99.6 ± 0.1% TMDAB 10:10:1 80 ± 0.5% 99.4 ± 0.1%TMDAB 15:15:1 74 ± 0.9% 98.4 ± 0.4% DMAPAP 3:3:1 78 ± 6.1% 87.1 ± 7.3%DMAPAP 5:5:1 81 ± 1.0% 98.4 ± 0.4% DMAPAP 10:10:1 69 ± 1.4% 96.0 ± 0.8%DMAPAP 15:15:1 62 ± 1.1% 94.4 ± 1.1% HMTETA 3:3:1 80 ± 4.0% 95.6 ± 1.5%HMTETA 5:5:1 80 ± 3.0% 98.4 ± 1.2% HMTETA 10:10:1 70 ± 1.3% 98.0 ± 1.0%HMTETA 15:15:1 65 ± 4.9% 98.2 ± 0.3% ^([a])Determined by ¹H NMRspectroscopy as discussed in Example 2.

It is apparent that an increase in the loading of the additive generallyresulted in an increase in the % THF separated from the aqueous solutionafter switching, as would be expected. It can also be seen that thediamine compound TMDAB at a 9 wt % loading (i.e. 5:5:1 THF:H₂O:amine)forced 87% of the THF out of the aqueous phase after switching while99.6% of the additive was retained in the aqueous phase. Even at a 3 wt% loading of TMDAB (15:15:1 THF:H₂O:amine), 74% of the THF was forcedout after switching. In comparison, the monoprotonated additives DMAEand MDEA were only effective at higher loadings and had greater lossesof the additive to the THF phase (Table 3).

In all experiments, the effect of the increase in ionic strength uponswitching with CO₂ could be reversed; such that the THF phase recombinedwith the aqueous phase to regenerate a one phase system when the mixturewas heated and sparged with N₂ or air to remove CO₂.

Example 4A Qualititative Determination of the Separation of SelectedCompound (THF) and Additive (Amine) Upon Switching at EquivalentAdditive Loadings

A qualitative comparison of reversible solvent switching in the fiveamine/water systems of Example 3 was undertaken at equivalent additiveloadings to determine by ¹H NMR spectroscopy the relative effectivenessof switching each additive from non-ionic amine to ionic ammoniumbicarbonate and back to non-ionic amine forms. Aqueous solutions (0.80molal) of DMAE, MDEA, TMDAB, THEED, DMAPAP, HMTETA additives were addedto 1:1 w/w solutions of THF:D₂O in NMR tubes, which were sealed withrubber septa. ¹H NMR spectra were acquired for each sample prior to anygas treatment, and are shown as the A spectra in FIGS. 4, 5, 6, and 7for DMAE, TMDAB, HMTETA and DMAPAP respectively. Two narrow gauge steelneedles were inserted and the trigger gas was gently bubble through oneof the needles into the solution at a rate of 4-5 bubbles per second.The second needle served as a vent for the gas phase, which wasmaintained at a positive pressure above atmospheric by the bubbling.

CO₂ was used as the trigger to switch the amine from its non-ionic toionic form. ¹H NMR spectra were acquired for each sample after switchingwith CO₂.

The spectrum obtained after switching DMAE by 20 minutes of bubbling at25° C. with a CO₂ trigger is shown as spectrum B in FIG. 4.Subsequently, the additive was switched back to non-ionic form bybubbling a nitrogen gas trigger through the solution for 300 minutes at75° C. and the spectrum is shown as spectrum C in FIG. 4.

The spectrum obtained after switching TMDAB by 30 minutes of bubbling at25° C. with a CO₂ trigger is shown as spectrum B in FIG. 5.Subsequently, the additive was switched back to non-ionic form bybubbling a nitrogen gas trigger through the solution for 240 minutes at75° C. and the spectrum is shown as spectrum C in FIG. 5.

The spectrum obtained after switching HMTETA by 20 minutes of bubblingat 25° C. with a CO₂ trigger is shown as spectrum B in FIG. 6.Subsequently, the additive was switched back to non-ionic form bybubbling a nitrogen gas trigger through the solution for 240 minutes at75° C. and the spectrum is shown as spectrum C in FIG. 6.

The spectrum obtained after switching DMAPAP by 20 minutes of bubblingat 25° C. with a CO₂ trigger is shown as spectrum B in FIG. 7.Subsequently, the additive was switched back to non-ionic form bybubbling a nitrogen gas trigger through the solution for 120 minutes at75° C. and the spectrum is shown as spectrum C in FIG. 7.

Example 4B Quantitative Determination of the Separation of SelectedCompound (THF) and Additive (Amine) Upon Switching at EquivalentAdditive Loadings

To measure the amount of THF being separated out of an aqueous phase byincreasing its ionic strength, and the amounts of amine which remainedin the aqueous phase, 1:1 w/w solutions of THF and water were preparedin graduated cylinders. The appropriate mass of amine additive to resultin a 0.80 molal solution was added and the cylinders were capped withrubber septa. After 30 minutes of bubbling CO₂ through the liquid phasefrom a single narrow gauge steel needle, a visible phase separation wasobserved. The two phases were a non-aqueous phase comprising THF, whichwas forced out of the increased ionic strength aqueous solution, and anaqueous phase comprising the additive in ionic form. The volumes of eachphase were recorded. Aliquots of the non-aqueous and aqueous layers weretaken and dissolved in d₃-acetonitrile in NMR tubes. A known amount ofethyl acetate was added to each NMR tube as an internal standard. ¹H NMRspectra were acquired as for the fully protonated additives, and throughintegration of the ethyl acetate standard, a concentration of THF oradditive was calculated and scaled up to reflect the total volume of theaqueous or non-aqueous phase giving a percentage of the compound beingforced out or retained. The results are shown in Table 4 below.

TABLE 4 Comparison of abilities of 0.80 molal aqueous solutions of amineadditives to separate THF from 1:1 w/w solutions of THF and H₂O andretention of amine additive in the aqueous phase when reacted with CO₂Additive % THF Separated^([a]) % Additive Retained^([a]) DMAE 70 ± 0.6%98.0 ± 0.2% MDEA 61 ± 0.6% 99.0 ± 1.3% TMDAB 82 ± 0.6% 99.2 ± 0.4%DMAPAP 79 ± 1.2% 98.8 ± 0.4% HMTETA 78 ± 0.9% 99.3 ± 0.4%^([a])Determined by ¹H NMR spectroscopy as discussed in Example 1.

Diamine TMDAB, triamine DMAPAP and tetramine HMTETA additives exhibitedsuperior THF separation compared to monoamine additives DMAE and MDEA.This observation can be explained due to the increase in ionic strengthas a result of the increased charge on the quaternary ammonium cationsresulting from the protonation of multiple basic nitrogen centres in thediamine, triamine and tetramine. It is apparent from equation (C) thatfor an equimolal concentration of additive, an increase in the charge onthe cation of the salt from +1 to +2 should give rise to a tripling inionic strength.

It should be noted that although TMDAB and DMPAP contain more than twotertiary amine centres, only two of the basic sites in each molecule arecapable of protonation as a result of switching with CO₂. This meansthat equimolal solutions of the protonated salts of TMDAB, DMAPAP andHMTETA should each exhibit a similar ionic strength, and thus similar %THF separations, as is apparent from Table 4.

Example 5 Reversible Protonation of Amine Additives in H₂O as Monitoredby Conductivity

Protonation of aqueous solutions of three tertiary amine additives,DMAE, MDEA, and THEED, in response to the addition of a CO₂ trigger wasperformed and monitored by conductivity meter.

Aqueous solutions of an additive with distilled, deionised H₂O wereprepared (1:1 v/v H₂O and DMAE, 1:1 v/v H₂O and MDEA and 1:1 w/w H₂O andTHEED) in sample beakers. 1:1 w/w H₂O and THEED was used because a 1:1v/v solution was too viscous to pour accurately. A trigger gas chosenfrom CO₂, air or nitrogen was bubbled at identical flow rates throughthe solution via a narrow gauge steel tube and the conductivity of thesolution was measured periodically using a Jenway 470 Conductivity Meter(Bibby Scientific, NJ, US) having a cell constant of 1.02 cm⁻¹.

Results of bubbling a CO₂ gas trigger through the solutions of additivesin water at room temperature are depicted in FIG. 7. As shown in thisFigure, the conductivity of each of the additive solutions rose as theamine was converted to its ionic form as it was contacted with the CO₂trigger. The aqueous solution of DMAE showed the largest rise inconductivity.

It is noted that conductivity is not simply a function of saltconcentration; conductivity is also strongly affected by a solution'sviscosity. Thus, even if two separate additive solutions have identicalnumbers of basic sites which can be fully protonated and have identicalconcentrations in water, they may have different conductivity levels.

The deprotonation reactions of the ionic solutions of additives in waterwere monitored in a similar manner, and the conductivity plot is shownin FIG. 8. Nitrogen gas was flushed through the solution at 80° C. toswitch salts back to their non-ionic tertiary amine form. The residuallevels of conductivity exhibited show that none of the additives werecompletely deprotonated by this treatment within 6 h.

Example 6 Reversible Protonation of Amine Additives in D₂O as Monitoredby ¹H NMR Spectroscopy

The degree of protonation of tertiary amine additives upon contact witha CO₂ trigger was investigated by ¹H NMR spectroscopy. Two monoamines,DMAE and MDEA, and the diamine THEED were chosen for study.

In order to establish the chemical shifts of the protonated bases, molarequivalents of several strong acids, including HCl and HNO₃, were addedto separate solutions of the amines dissolved in D₂O. ¹H NMR spectrawere acquired on a Bruker AV-400 NMR spectrometer at 400.3 MHz for threereplicate solutions of each amine. An average value of each chemicalshift for each protonated base was calculated along with standarddeviations. If the bases when reacted with the trigger to ionic formshowed chemical shifts within this error range, they were considered tobe 100% protonated within experimental error. The ¹H NMR chemical shiftsof the unprotonated amines were also measured.

The extent of protonation by CO₂ of each additive at room temperature at0.5 M (except THEED was at 0.1 M) in D₂O was monitored by ¹H NMR. Theamine was dissolved in D₂O in an NMR tube and sealed with a rubbersepta. The spectrum was then acquired. Subsequently, two narrow gaugesteel needles were inserted and gas was gently bubbled through one ofthem into the solution at approximately 4-5 bubbles per second. Thesecond needle served as a vent for the gaseous phase.

Firstly CO₂ was bubbled through the solution for the required length oftime and then the spectrum was re-acquired. This process was repeated.The % protonation of the amine was determined from the observed chemicalshifts by determining the amount of movement of the peaks from thenormal position for the unprotonated amine towards the position expectedfor the fully protonated amine.

The results shown in FIG. 9 indicate that DMAE and MDEA are fullyprotonated (the peaks fell within the standard deviation of the HCl andHNO₃ salts) within 20 minutes when CO₂ was bubbled through the solution.THEED is one half protonated (49%) by 10 minutes, meaning that only oneof the two nitrogen atoms of this diamine has been protonated.

The reverse reaction was monitored in a similar manner and the resultsshown in FIG. 10. Nitrogen gas was flushed through the solution at 75°C. The spectra showed that none of the additives were completelydeprotonated by this treatment within 5 hours, (2 hours for THEED), withthe ionic form of THEED reacting the fastest of the three, and with DMAEbeing the slowest. THEED was 98% deprotonated (i.e., the ionic strengthof the solution dropped twenty-five fold) after 2 hours of N₂ bubbling.

The observed rates of switching, as represented by the protonation anddeprotonation processes, are affected by the manner in which the CO₂ orsparging gas was introduced (e.g., its rate of introduction and theshape of the vessel containing the solution). For example, a comparisonof FIG. 7 with FIG. 9 shows that the rate of the reaction in the ¹H NMRexperiment was faster than that in the conductivity experiment. Thisrate difference is due to the difference in equipment. The ¹H NMRexperiment was performed in a tall and narrow NMR tube, which is moreefficiently flushed with CO₂ than the beaker used in the conductivitytests. Furthermore, it is very likely that the rate of deprotonation andthus reduction in the ionic strength of the solution could be increasedif the N₂ sparging were done in a more efficient manner than simplebubbling through a narrow gauge tube.

Thus, a 1:1 v/v mixture of MDEA and water can be taken to 100%protonated and returned back to about 4.5% protonation bybubbling/sparging with N₂. It is possible to calculate an approximateionic strength of the 100% and 4.5% degrees of protonation of the amineadditive. The density of MDEA is 1.038 g/mL, so a 1 L sample of thismixture would contain 500 g of water and 519 g (4.4 mol) MDEA. Thereforethe concentration of MDEA is 4.4 M. The ionic strength, assuming anideal solution and assuming that the volume does not change when CO₂ isbubbled through the solution, is 4.4 M at 100% protonation and 0.198 Mat 4.5% protonation (using equation (A) above).

Example 7 Reversible Protonation of Amine Additives in H₂O as Monitoredby Conductivity

Three tertiary polyamine additives were selected for furtherinvestigation of additives for switchable ionic strength aqueoussolutions. TMDAB is a diamine, DMAPAP is a triamine, and HMTETA is atetramine.

1:1 v/v solutions of the various additives and distilled, deionisedwater were prepared in six dram glass vials and transferred to a frittedglass apparatus which acted as a reaction vessel. The fritted glassapparatus consisted of a long narrow glass tube leading to a fine glassfrit having a diameter of approximately 4 cm. The other end of the glassfrit was connected to a cylindrical glass tube which held the solutionof the additive during contacting with the trigger gas. This apparatusallowed a multiple source of trigger gas bubbles to contact thesolution, compared to the single point source of Example 5.

A trigger gas chosen from CO₂, air or nitrogen was bubbled through thesolution via the glass frit at a flow rate of 110 mL min⁻¹ as measuredby a J&W Scientific ADM 2000 Intelligent Flowmeter (CA, USA). For eachconductivity measurement, the solution was transferred back to a sixdram vial, cooled to 298 K and measured in triplicate. Conductivitymeasurements were performed using a Jenway 470 Conductivity Meter (BibbyScientific, NJ, US) having a cell constant of 1.02 cm⁻¹.

FIG. 11 shows a plot of the conductivity changes resulting from bubblingCO₂ through the three solutions at 25° C. It is apparent that HMTETA (▪)and DMAPAP (▴), the tetramine and triamine respectively, exhibit lowerconductivities than TMDAB (♦), the diamine. In addition, TMDAB exhibitsthe highest rate of conductivity increase.

The reverse reaction was monitored in a similar manner and the resultsshown in FIG. 12. Nitrogen gas was flushed through the solution at 80°C. It is apparent that the conductivity of the solution of HMTETA (▪) inionic form returns to close to zero after 20 minutes, indicatingsubstantial removal of CO₂ from the solution and reversion of theadditive to its non-ionic form. The rate of conductivity decrease ishighest for TMDAB (♦), the diamine, indicating it can be reversiblyswitched between non-ionic and ionic forms at a higher rate than HMTETAand DMAPAP (▴)

The observed rates of switching, as represented by the changes inconductivity, appear to be affected by the manner in which the CO₂ orsparging gas was introduced (e.g., its rate of introduction and theshape of the vessel containing the solution). For example, a comparisonof FIG. 11 with FIG. 7 shows that the rate of the reaction utilising thefritted gas apparatus appears to be faster than that the delivery of thetrigger via a narrow gauge steel tube, although it is accepted thatdifferent additives are being compared. This may be because the frittedglass apparatus is more efficiently flushed with CO₂ than the beakerused in the conductivity tests.

Example 8 Emulsion Formation and Disruption of Solutions Comprising aSurfactant and Switchable Amine Additive

Three vials were prepared, each containing 0.462 gN,N,N′,N′-tetramethyl-1,4-diaminobutane (TMDAB) in 4 mL water (giving a0.80 molal solution) and 20 mg SDS (sodium dodecyl sulfate, anonswitchable surfactant) at 0.50 wt % loading. To each vial n-decanol(0.25 mL) was added and the vials were capped with rubber septa. FIG.13, photograph “A” shows the three vials at this stage in theexperiment. In each vial, there are two liquid phases. The lower liquidaqueous phase has a larger volume and is transparent and colourless. Theupper liquid n-decanol phase has a smaller volume and is also colourlessthough is not as transparent. n-Decanol is not miscible with neat water.

The three vials were then shaken by hand for 30 seconds. FIG. 13,photograph “B” shows the appearance after the shaking. All three vialsshow an opaque liquid mixture with cloudiness and foaming typical of anemulsion, which is as expected because of the presence of the knownsurfactant SDS.

Gases were then bubbled through the solutions for 30 min via a narrowgauge steel needle inserted through the septum and down into the liquidmixture. For each vial, gas was allowed to vent out of the vial via ashort second needle inserted into the septum but not into the liquidphase. The gas was CO₂ for the left vial and N₂ for the centre and rightvials. FIG. 13, photograph “C” shows the appearance after the treatmentwith gas. Only the right two vials show the cloudiness typical of anemulsion. The liquid in the left vial is now clear and free of foam,showing that the conversion of the aqueous solution to its high-ionicstrength form has greatly weakened the ability of the SDS to stabilizeemulsions and foams. The liquid contents of the centre and right vialsstill show the cloudiness and foaminess typical of an emulsion,indicating that bubbling N₂ gas through the solution does not have theeffect of weakening the ability of SDS to stabilize emulsions and foams.This is because N₂ had no effect on the ionic strength of the aqueousphase.

While the left vial was allowed to sit for 30 min without furthertreatment, CO₂ gas was bubbled through the liquid phase of the centrevial for 30 min and N₂ was bubbled through the right vial. FIG. 13,photo “D” shows the appearance of the three vials after this time. Theliquids in the left and centre vials are now largely clear and free offoam, showing that the conversion of the aqueous solution to itshigh-ionic strength form has greatly weakened the ability of the SDS tostabilize emulsions and foams. The emulsion and foam still persist inthe right vial.

N₂ gas was bubbled through the liquid phases of the left and centrevials for 90 min in order to remove CO₂ from the system and therebylower the ionic strength of the aqueous solution. The two vials werethen shaken for 30 min. During this gas treatment and shaking, the rightvial was left untouched. FIG. 13, photograph “E” shows the appearance ofthe three vials after this time. All three exhibit the cloudinesstypical of an emulsion, although foaminess in the left two vials is notevident, presumably because the conversion of the aqueous solution backto a low ionic strength is not complete. In practice, substantialconversion to low ionic strength is not difficult. However, it can bemore difficult to achieve complete conversion.

Example 9 Description of Ionic Strength

The ionic strength of an aqueous solution of the salt will varydepending upon the concentration of the salt and the charge on theammonium ion. For example, an amine B having n sites which can beprotonated by carbonic acid to provide a quaternary ammonium cation offormula [BH_(n) ^(n+)], may have a switching reaction shown in reaction(1):

B+nH₂O+nCO₂⇄[BH_(n) ^(n+) ]+n[ ^(−O) ₃CH]  reaction (1)

If the molality of the amine in aqueous solution is m, the ionicstrength I of the ionic solution after switching can be calculated fromequation (C):

I=½m(n ² +n)  (C)

Thus, for a given molality m, the ionic strength of a diprotonateddiamine (n=2) will be three times that of a monoprotonated monoamine(n=1). Similarly, the ionic strength of a triprotonated triamine (n=3)will be six times that of that of a monoprotonated monoamine and theionic strength of a tetraprotonated tetramine (n=4) will be ten timesthat of a monoprotonated monoamine. Thus, by increasing the number oftertiary amine sites in the compound of formula (1) which can beprotonated by the trigger, the ionic strength of a solution comprisingthe corresponding salt of formula (2) can be increased, for a givenconcentration.

Not all the basic sites on a compound of formula (1) may be capable ofprotonation by a gas which generates hydrogen ions in contact withwater. For instance, when the gas is CO₂, the equilibrium between CO₂and water and the dissociated carbonic acid, H₂CO₃ is shown in reaction(2):

CO₂+H₂O⇄H⁺+HCO₃ ⁻  reaction (2)

The equilibrium constant, K_(a) for this acid dissociation is calculatedfrom the ratio

$\frac{\left\lbrack H^{+} \right\rbrack \left\lbrack {HCO}_{3}^{-} \right\rbrack}{\left\lbrack {CO}_{2} \right\rbrack}$

at equilibrium—in dilute solutions the concentration of water isessentially constant and so can be omitted from the calculation. Theequilibrium constant K_(a) is conventionally converted into thecorresponding pK_(a) value by equation (D):

pK _(a)=−log K _(a)  (D)

The pK_(a) for reaction (2) is 6.36. The corresponding equilibrium forthe dissociation of a protonated amine base BH⁺ (i.e. the conjugateacid) is provided by reaction (3),

BH⁺⇄H⁺+B  reaction (3)

The equilibrium constant K_(aH), for the conjugate acid BH⁺ dissociationis calculated by the ratio

$\frac{\lbrack B\rbrack \left\lbrack H^{+} \right\rbrack}{\left\lbrack {BH}^{+} \right\rbrack}.$

The equilibrium constant K_(aH) is conventionally converted into thecorresponding pK_(aH) value analogously to equation (D). From theforegoing, it will be apparent that the equilibrium constant for theswitching reaction shown in reaction (1) above in which n=1 can becalculated from the ratio

$\frac{\left\lbrack {BH}^{+} \right\rbrack \left\lbrack {HCO}_{3}^{-} \right\rbrack}{\lbrack B\rbrack \left\lbrack {CO}_{2} \right\rbrack},$

which is equivalent to

$\frac{K_{a}}{K_{aH}}.$

The ratio

$\frac{K_{a}}{K_{aH}}$

can also be expressed in terms of the corresponding pK values as 10^(pK)^(aH) ^(−pK) ^(a) . Thus, in the case of the dissociation of CO₂ inwater, if the pK_(aH) value of the conjugate acid BH⁺ exceeds 6.36, theratio

$\frac{\left\lbrack {BH}^{+} \right\rbrack \left\lbrack {HCO}_{3}^{-} \right\rbrack}{\lbrack B\rbrack \left\lbrack {CO}_{2} \right\rbrack}$

is greater than 1, favoring the production of ammonium bicarbonate.Thus, it is preferred that a salt as used herein comprises at least onequaternary ammonium site having a pK_(aH) greater than 6 and less than14. Some embodiments have at least one quaternary ammonium site having apK_(aH) in a range of about 7 to about 13. In some embodiments the saltcomprises at least one quaternary ammonium site having a pK_(aH) in arange of about 7 to about 11. In other embodiments, the salt comprisesat least one quaternary ammonium site having a pK_(aH) in a range ofabout 7.8 to about 10.5.

Example 10 Synthesis of Diamine and Triamine Switchable AdditivesExample 10A Synthesis of N,N,N′,N′-tetraethyl-1,4-diaminobutane (TEDAB)

4.658 g (63.4 mmol) diethylamine was dissolved in 100 mL dichloromethaneand cooled to 0° C. 2.339 g (15.1 mmol) succinyl chloride was addeddropwise to the solution. The solution was warmed to room temperatureand stirred for 18 hours.

An aqueous solution 0.80 mL concentrated HCl and 25 mL H₂O was added tothe mixture to wash the organic layer. The organic layer was thenremoved and dried with MgSO₄. The solvent was removed in vacuo to yield3.443 g of N,N,N′,N′-tetraethylsuccinamide in 99% yield. ¹H NMR (400 MHzCDCl₃) −δ: 3.37 (q, =7 Hz, 8H), 2.69 (s, 4H), 1.20 (t, J=7 Hz, 6H), 1.11(t, J=7 Hz, 6H).

3.443 g (15.1 mmol) of N,N,N′,N′-tetraethylsuccinamide is dissolved in100 mL THF, degassed with N₂ and cooled to 0° C. 61.0 mL of 2.0M LiAlH₄in THF solution (122 mmol) was added dropwise to the solution. Thesolution was then refluxed for 6 hours.

The solution was then cooled to 0° C. and the excess LiAlH₄ was quenchedby adding 4.6 mL H₂O, 4.6 ml, 15% NaOH, and 13.8 mL H₂O. The solutionwas warmed to room temperature and stirred for 12 hours. The precipitatewas filtered off and washed with THF. The washings were combined withthe original THF solution and dried with MgSO₄. The solvent was removedin vacuo to yield 2.558 g of a brown liquid resulting in a 84.6% yieldof N,N,N′,N′-tetraethyl-1,4-diaminobutane. ¹H NMR (400 MHz CDCl₃) −δ:2.55 (q, =7 Hz, 8H), 2.41 (t, J=7 Hz, 4H), 1.43 (t, J=7 Hz, 4H), 1.02(t, J=7 Hz, 12H).

All other straight chain diamines,N,N,N′,N′-tetrapropyl-1,4-diaminobutane andN,N′-diethyl-N,N′-dipropyl-1,4-diaminobutane, were synthesized in asimilar fashion utilizing the appropriate starting materials. Succinylchloride, diethylamine, dipropylamine, lithium aluminum hydride solutionwere all purchased from Sigma Aldrich and used as received.N-ethylpropylamine was purchased from Alfa Aesar and the solvents andMgSO₄ were purchased from Fisher and used as received.

Example 10B Synthesis of1,1′,1″-(cyclohexane-1,3,5-triyl)tris(N,N-dimethylmethanamine) (CHTDMA)

1.997 g (9.2 mmol) 1,3,5-cyclohexane-tricarboxylic acid was taken up in40 mL dichloromethane to create a suspension. 3.84 g (29.8 mmol) oxalylchloride and one drop of DMF were added to the solution. The solutionwas refluxed for 3 hours, giving a yellow solution with whiteprecipitate. The mixture was cooled to room temperature and the solventwas removed in vacuo resulting in 2.509 g of a solid which containedboth the desired 1,3,5-cyclohexane tricarbonyl trichloride and unwantedsalts. ¹H NMR (400 MHz CDCl₃) −δ: 2.88 (t, J=9 Hz, 3H), 2.69 (d, J=13Hz, 3H), 1.43 (q, J=13 Hz, 3H).

2.509 g of the solid mixture was taken up in 50 mL THF and cooled to 0°C. 34.5 mL of a 2.0 M dimethylamine solution in THF (69 mmol) was added.The solution was warmed to room temperature and stirred for 18 hours.The solvent was then removed in vacuo leaving a yellow solid. The solidwas taken up in a solution of 2.081 g (37.1 mmol) KOH in 20 mL H₂O.Organic contents were then extracted with 3×40 mL chloroform washings.The organic washings were collected and the solvent removed in vacuo toyield 1.930 g of a yellow liquid,N,N,N′,N′,N″,N″-hexamethylcyclohexane-1,3,5-tricarboxamide in 70.2%yield. ¹H NMR (400 MHz CDCl₃) −δ: 3.06 (s, 9H), 2.92 (s, 9H), 2.65 (q,J=15 Hz, 3H), 1.86 (t, J=8 Hz, 6H).

1.930 g (6.5 mmol) ofN,N,N′,N′,N″,N″-hexamethylcyclohexane-1,3,5-tricarboxamide was dissolvedin 80 mL THF and cooled to 0° C. 42.0 mL of 2.0M LiAlH₄ in THF solution(84 mmol) was added dropwise to the solution. The solution was thenrefluxed for 6 hours.

The solution was then cooled to 0° C. and the excess LiAlH₄ was quenchedby adding 3.2 mL H₂O, 3.2 mL 15% NaOH, and 9.6 mL H₂O. The solution waswarmed to room temperature and stirred for 12 hours. The precipitate wasfiltered off and washed with THF. The washings were combined with theoriginal solution and dried with MgSO₄. The solvent was removed in vacuoto yield 1.285 g of a yellow liquid resulting in a 54.4% yield of1,1′,1″-(cyclohexane-1,3,5-triyl)tris(N,N-dimethylmethanmine). ¹H NMR(400 MHz CDCl₃) −δ: 2.18 (s, 18H), 2.07 (d, J=7 Hz, 8H), 1.89 (d, J=12Hz, 3H), 1.52, (m, J=7 Hz, 3H), 0.48 (q, J=12 Hz, 3H). M⁺=255.2678,Expected=255.2674.

Other cyclic triamines, N,N,N′,N′,N″,N″-1,3,5-benzenetrimethanamine,were synthesized in a similar fashion utilizing the appropriate startingmaterials. 1,3,5-benzenetricarbonyl trichloride was purchased from SigmaAldrich and used as received. 1,3,5-cyclohexanetricarboxylic acid waspurchased from TCI and used as received.

Example 11 Controlling the Zeta Potential of Suspended Clay Particles inWater

In a suspension of solid particles in a liquid, a zeta potential near tozero indicates that the particles have little effective surface chargeand therefore the particles will not be repelled by each other. Theparticles will then naturally stick to each other, causing coagulation,increase in particle size, and either settle to the bottom of thecontainer or float to the top of the liquid. Thus the suspension willnot normally be stable if the zeta potential is near zero. Thereforehaving the ability to bring a zeta potential close to zero is useful fordestabilizing suspensions such as clay-in-water suspensions. However,strategies such as addition of calcium salts or other salts aresometimes undesirable because, while these strategies do cause thedestabilization of suspensions, the change in water chemistry isessentially permanent; the water cannot be re-used for the originalapplication because the presence of added salts interferes with theoriginal application. Therefore there is a need for a method fordestabilizing suspensions that is reversible.

Experimental Methods:

Clay fines were weighed and placed into individual vials (0.025 g,Ward's Natural Science Establishment). Kaolinite and montmorillonitewere used as received, but illite clay was ground into a powder using amortar and pestle. Solutions containing additives were made withdeionized water (18.2 MΩ/cm, Millipore) and 10 mL was added to the clayfines. A suspension was created using a vortex mixer and subsequentlydispensed into a folded capillary cell. The zeta potential was measuredusing a Malvern Zetasizer instrument. The errors reported on the zetapotential values were the standard deviations of the zeta potentialpeaks measured.

Unless specified, all carbon dioxide treatments were conducted with theaqueous solutions prior to addition to the clay fines. For applicablemeasurements, ultra pure carbon dioxide (Supercritical CO₂Chromatographic Grade, Paxair) was bubbled through the solutions using asyringe.

Results: Illite

Additive Zeta Potential (mV) 0.8 molal BDMAPAP −19.1 ± 3.92 0.8 molalBDMAPAP + 1 h CO₂ −1.87 0.8 molal TMDAB −26.0 ± 3.92 0.8 molal TMDAB + 1h CO₂ −4.56 1 mM TMDAB −39.5 ± 6.32 1 mM TMDAB + 1.5 hour CO₂ −4.69 ±4.23 10 mM TMDAB −48.2 ± 7.44 10 mM TMDAB + 1.5 hour CO₂ −3.12 ± 7.16

Kaolinite

Additive Zeta Potential (mV) 0.8 molal BDMAPAP −24.3 ± 2.29 0.8 molalBDMAPAP + 1 h CO₂ −3.99 0.8 molal TMDAB −17.4 ± 3.92 0.8 molal TMDAB + 1h CO₂   2.29 1 mM TMDAB −39.6 ± 6.68 1 mM TMDAB + 1.5 hour CO₂ −5.03 ±4.46 10 mM TMDAB −50.7 ± 13.1 10 mM TMDAB + 1.5 hour CO₂ −3.35 ± 8.49

Montmorillonite

Additive Zeta Potential (mV) 0.8 molal BDMAPAP −16.8 ± 4.64 0.8 molalBDMAPAP + 1 h CO₂ −2.99 0.8 molal TMDAB −25.8 ± 4.14 0.8 molal TMDAB + 1h CO₂ −5.52 1 mM TMDAB −40.2 ± 6.87 1 mM TMDAB + 1.5 hour CO₂ −3.20 ±4.61 10 mM TMDAB −23.6 ± 5.68 10 mM TMDAB + 1.5 hour CO₂   9.07 ± 4.18

For three of the clays tested, it was found that switchable wateradditives TMDAB and BDMAPAP were effective additives for changing clayzeta potentials. Upon addition of CO₂, the absolute values of the clayzeta potentials were reduced. This effect was observed even at lowconcentrations of the switchable water additive (1 mM).

The data above demonstrates the ability of switchable water to affectthe zeta potential of clay suspensions, however, the CO₂ treatments wereconducted on the aqueous solutions of TMDAB before the clay fines wereadded (a method referred to as “switching externally”). Anotherexperiment was performed in which CO₂ was bubbled through a 1 mM aqueoussolution of TMDAB that already contained clay fines (a method referredto as “switching in situ”). The results with kaolinite clay aresummarized in the table below.

Kaolinite clay

Zeta Potential (mV) Switching Switching externally in situ 1 mM TMDAB−39.6 ± 6.68 −38.9 ± 8.69 1 mM TMDAB + 1 h CO₂ −5.03 ± 4.46 −0.31 ± 4.151 mM TMDAB + 1 h CO₂ + 1.5 h N₂ −25.0 ± 5.84 −32.5 ± 6.38 at 70° C.

It was observed that the magnitude of the zeta potential of the claysurfaces decreased regardless of whether the switching externally methodor the switching in situ method was used. In addition, the zetapotential could be restored to its original value upon treatment withnitrogen gas at 70° C.

Example 12 Reversible Destabilization of a Clay-in-Water Suspension

Three variations of clay settling experiments were conducted with 1 mMTMDAB (TCI America, Batch FIB01) to elucidate the ability of thisswitchable ionic strength additive to affect stability of claysuspensions.

Experiment 1

As depicted in FIG. 14A, Kaolinite clay fines (5 g) were added to 100 mLof 1 mM TMDAB in deionized water. The mixture was stirred for 15 minutesat 900 rpm prior to transferring into a 100 mL graduated cylinder, whichwas subsequently sealed with a rubber septum. Settling of the clay fineswas monitored as a function of time using a cathetometer.

CO₂ was bubbled through 100 mL of 1 mM TMDAB using a dispersion tube for1 hour. Kaolinite fines (5 g) were added to the aqueous solution and themixture was stirred for 15 minutes at 900 rpm prior to transferring intoa 100 mL graduated cylinder and sealing with a rubber septum. Settlingof clay fines was monitored. CO₂ was bubbled through 100 mL of 1 mMTMDAB using a dispersion tube for 1 hour. The solution was heated to 70°C. and N₂ was bubbled through for 1 hour. After cooling to roomtemperature, kaolinite fines (5 g) were added and the mixture wasstirred 900 rpm for 15 minutes prior to transferring into a 100 mLgraduated cylinder and sealing with a rubber septum. Settling of clayfines was monitored.

Experiment 2

As depicted in FIG. 14B, Kaolinite clay fines (5 g, Ward's NaturalScience Establishment) were added to 100 mL of 1 mM TMDAB in deionizedwater. The mixture was stirred for 15 minutes at 900 rpm prior totransferring into a 100 mL graduated cylinder, which was subsequentlysealed with a rubber septum. Settling of the clay fines was monitored asa function of time.

CO₂ was bubbled through the suspension above. The mixture was stirredfor 15 minutes at 900 rpm prior to transferring into a 100 mL graduatedcylinder, which was subsequently sealed with a rubber septum. Settlingof the clay fines was monitored.

The clay fines above were resuspended in the solution and the mixturewas heated to 70° C. N₂ was bubbled through for 1 hour. After cooling toroom temperature, the mixture was stirred 900 rpm for 15 minutes priorto transferring into a 100 mL graduated cylinder and sealing with arubber septum. Settling of clay fines was monitored.

Experiment 3

As depicted in FIG. 14C, Kaolinite clay fines (5 g, Ward's NaturalScience Establishment) were added to 100 mL of 1 mM TMDAB in deionizedwater. The mixture was stirred for 15 minutes at 900 rpm prior totransferring into a 100 mL graduated cylinder, which was subsequentlysealed with a rubber septum. Settling of the clay fines was monitored asa function of time.

The suspension above was filtered. CO₂ was bubbled through the filtratefor 1 hour. Kaolinite clay fines (4.5 g) were added and the mixture wasstirred for 15 minutes at 900 rpm prior to transferring into a 100 mLgraduated cylinder, which was subsequently sealed with a rubber septum.Settling of clay fines was monitored.

Control Experiment

CO₂ was bubbled through 100 mL of deionized water for 1 h. Kaoliniteclay (5 g) was added and the mixture was stirred for 15 minutes at 900rpm prior to transferring into a 100 mL graduated cylinder, which wassubsequently sealed with a rubber septum. Settling of clay fines wasmonitored.

Results

Experiment 1 was conducted to examine the effect of the switchable wateradditive on the settling behavior of clay. The switching was conductedin the absence of clay to ensure that the switching occurred fullywithout any impedance from the clay. The results are plotted in FIGS.15A-C.

A stable suspension was formed with kaolinite clay and 1 mM TMDAB.However, kaolinite clay with 1 mM of CO₂ treated TMDAB resulted in thesettling of clay with a clean supernatant and a clear sediment line. Astable suspension was also formed with kaolinite clay and 1 mM of TMDABtreated for 1 hour with CO₂ followed by 1 hour of N₂ treatment.Photographs were taken after each 1 hour treatment and are provided inFIG. 15D.

Experiment 2 was conducted to examine if the switchable water additiveswould still switch upon addition of CO₂ in the presence of kaoliniteclay.

Kaolinite clay and 1 mM TMDAB were initially mixed to give a stablesuspension. This suspension was treated with CO₂, which resulted in thesettling of the clay fines with a clean supernatant and a clear sedimentline. As shown in FIGS. 16A-B, the behavior observed was exactly as thatobserved for Experiment 1. The settled clay was stirred to reform asuspension, which was treated with N₂, after which the suspension wasstable. Experiment 3 was conducted to determine if the switchable ionicstrength additive adheres to the clay surface and would therefore belost upon removal of the clay. The suspension created with the CO₂treated filtrate settled much like the previous two experiments. A clearsediment line was observed, however, the liquid above the sediment linewas turbid and still contained clay fines (See, FIGS. 17A and C). Thisbehavior was also observed with deionized water treated with CO₂ in theabsence of any switchable water additive (See, FIGS. 17B and C).

Example 13 The Removal of Water from an Organic Liquid

2.710 g THF (3.76×10⁻² mol) and 0.342 g H₂O (1.90×10⁻² mol) were mixedtogether in a graduated cylinder to create a single phase solution ofroughly 8:1 THF:H₂O (w/w). 0.109 g (7.56×10⁻⁴ mol) ofN,N,N′N′-tetramethyl-1,4-diaminobutane (TMDAB) was added to the solutionagain generating a single phase solution. The THF:TMDAB ratio wasapproximately 25:1 (w/w). This solution containing three components hada mol % composition as follows: 65.6 mol % THF, 33.1 mol % H₂O, and 1.3mol % TMDAB.

A stir bar was added to the solution in the graduated cylinder and thecylinder was capped with a rubber septa. A long narrow gauge steelneedle was inserted through the septa and into the solution. A secondneedle was pushed through the septa but not into the solution. CO₂ wasbubbled into the solution through the first steel needle at a flow rateof about 5 mL min⁻¹ with stirring of ˜300 RPM for 30 minutes. At the endof the bubbling a clear, colourless aqueous phase at the bottom of thecylinder had creamed out of the original organic phase. The organicphase was separated from the aqueous phase by decantation.

76.1 mg of the top organic phase was extracted and placed in an NMRtube. The sample was diluted with deuterated acetonitrile and 32.3 mg ofethyl acetate was added to act as an internal standard. A ¹H NMRspectrum was acquired. Using the integration of the NMR signals of theH₂O and TMDAB compared to those of the known amount of ethyl acetateadded, calculated masses of 4.58 mg and 0.46 mg of H₂O and TMDAB wereacquired respectively. The remaining mass of 71.06 mg corresponds to theTHF in the sample.

The “dried” organic THF phase had a mol % composition as follows: 79.3mol % THF, 20.5 mol % H₂O and 0.3 mol % TMDAB.

Example 14 Use of a Switchable Additive to Expel an Organic Compound Outof Water and then the Removal of Much of the Additive from the AqueousPhase

In some embodiments, the non-ionized form of the additive iswater-immiscible. This makes it possible to create high ionic strengthin the water, while CO₂ is present, in order to achieve some purposesuch as the expulsion of an organic compound from the aqueous phase andthen, by removing the CO₂, to recover the majority of the additive fromthe water. Here we describe the expulsion of THF from a water/THFmixture and subsequent recovery of much of the additive from the water.

1.50 g H₂O, 1.50 g THF, and 0.30 g N,N,N′N′-tetraethyl-1,4-diaminobutane(TEDAB) were mixed together in a graduated cylinder to generate a singlephase solution. The solution had a total volume of 3.54 mL. A small stirbar was added to the solution and the cylinder was capped with a rubbersepta. The following procedure was run in triplicate with a new sample(of the same contents shown above) each time.

A long, narrow gauge needle was inserted through the septa into thesolution. A second small needle was inserted into the septa but not intothe solution itself. CO₂ was bubbled through the solution a flow rate ofabout 5 ml/min for 45 minutes with stirring until a 2^(nd) phase creamsout on top of the aqueous phase. The CO₂ bubbling was stopped and theneedles withdrawn. The cylinder was immersed in a hot water bath forseveral seconds to facilitate the separation of the liquid phases. Bothphases were clear and yellow in colour. The top organic layer had avolume of 1.50 mL and the remaining aqueous layer had a volume of 2.04mL.

The organic phase was decanted off giving a mass of 1.253 g(density=0.84 g/mL). The aqueous phase had a mass of 1.94 g(density=0.98 g/mL) resulting in a loss of 0.12 g due to transferring ofsolutions or blow-off.

A 39.1 mg sample of the organic phase was placed in an NMR tube withdeuterated acetonitrile and 50.2 mg ethyl acetate to act as an internalstandard. A 66.2 mg sample of the aqueous phase was placed in a 2^(nd)NMR tube with deuterated acetonitrile with 22.3 mg ethyl acetate to actas an internal standard. A ¹H NMR spectra was acquired and knowing thecorresponding amount of ethyl acetate in each sample the resultingamounts of THF in the aqueous sample and additive in the organic samplecan be calculated. Knowing the mass, volume, and density of each layer,the total amount of THF or additive in a respective layer can becalculated.

It was found that an average of 77.2±3.5% THF was removed from theaqueous phase with 91.1±3.7% of the TEDAB residing in the aqueous phase.

1.943 g (1.90 mL) of the aqueous phase was returned to the samegraduated cylinder. The needles and septa were put back into thecylinder and the cylinder was immersed in a 60° C. water bath. N₂ wasintroduced in the same fashion as CO₂ performed previously and the N₂was bubbled through the solution for 90 minutes causing a deep yelloworganic phase to cream out of the aqueous phase.

The new organic phase had a volume of 0.17 mL leaving an aqueous phaseof 1.57 mL. The organic layer was decanted off giving a mass of 0.09 gwhile the remaining aqueous phase had a mass of 1.507 g (density=0.96g/mL). A 37.9 mg sample of the aqueous phase was taken up in an NMR tubewith deuterated acetonitrile and 41.5 mg ethyl acetate to act as aninternal standard. A ¹H NMR spectra was acquired and using the sameprocedure of comparing integrations as performed above, it was foundthat 49.3±6.3% of the TEDAB was removed from the aqueous phase. It wasalso found that the overall 90.0±2.1% of the total THF had been removedfrom the aqueous phase at the end of the procedure.

Using N,N′-diethyl-N,N′-dipropyl-1,4-diaminobutane instead ofN,N,N′N′-tetraethyl-1,4-diaminobutane (TEDAB) in the above procedurecaused the expulsion of 68% of the THF from the aqueous phase after CO₂treatment. After N₂ treatment of the separated aqueous phase, 81% of theN,N′-diethyl-N,N′-dipropyl-1,4-diaminobutane was removed from theaqueous phase.

Example 15 Determining the Miscibility of Several Diamines and Triamineswith Water in the Presence and Absence of CO₂

In some embodiments, the non-ionized form of the additive iswater-immiscible while the charged form is water-miscible orwater-soluble. The following experiments were performed in order toidentify whether certain diamines and triamines have this phasebehavior.

A 5:1 w/w solution of water and the liquid additive (total volume 5 mL)were mixed together in a glass vial at room temperature. Whether themixture formed one or two liquid phases was visually observed. Then CO₂was bubbled through the mixture via a single narrow gauge steel needleat a flow rate of ˜5 mL min⁻¹ for 90 min. Whether the mixture formed oneor two phases was visually observed. The results were as follows:

Before addition After addition Additive of CO₂ of CO₂1,3,5-C₆H₃(CH₂NMe₂)₃ miscible miscible 1,3,5-cycloC₆H₉(CH₂NMe₂)₃immiscible miscible Et₂NCH₂CH₂CH₂CH₂NEt₂ immiscible misciblePrEtNCH₂CH₂CH₂CH₂NPrEt immiscible miscible Pr₂NCH₂CH₂CH₂CH₂NPr₂immiscible immiscible

Example 16 Preparation and Use of a Polyamine for Expulsion ofAcetonitrile from Water Example 16A Preparation of the Polyamine

Polyethyleneimine samples of three different molecular weights (M.W.600, 99%; M.W. 1800, 99%; and M.W. 10,000, 99%) were purchased from AlfaAesar. Formaldehyde (37% in H₂O) and formic acid were purchased fromSigma-Aldrich. All reagents were used without further purification.Amberlite™ IRA-400 (OH) ion exchange resin was purchased from Supelco.

For the samples using polyethyleneimine M.W. 600 and 1800: A 250 mLround bottom flask was equipped with a 2 cm teflon stirring bar andplaced over a magnetic stirring plate. 1.8 g (M.W. 600: 41.9 mmol, 1 eq,M.W. 1800: 41.9 mmol, 1 eq) of the polyethyleneimine were placed in theflask and 9.73 mL (120 mmol: M.W. 600: 40 eq and M.W. 1800 120 eq)formaldehyde solution and 4.53 mL (120 mmol: M.W. 600: 40 eq and M.W.1800 120 eq) formic acid were added. The flask was equipped with acondenser and the reaction mixture was heated to 60° C. for 16 hour withan oil bath. After 16 hour the mixture was allowed to cool to roomtemperature and the solvents were removed under reduced pressure. Then,the crude product was dissolved in 20 mL EtOH anhydrous and 4 g ofAmberlite resin was added to the solution. The resulting mixture wasstirred for 4 hour or for 16 hour at room temperature before the resinwas filtered of and the EtOH was removed under reduced pressure. Themethylated polymer was obtained as a dark yellow oil (1.8 g from theM.W. 600 sample and 1.7 g from the M.W. 1800 sample).

For the sample using polyethyleneimine M.W. 10,000: A 250 mL roundbottom flask was equipped with a 2 cm teflon stirring bar and placedover a magnetic stirring plate. 1.8 g (41.9 mmol, 1 eq) of thepolyethyleneimine were placed in the flask and 9.73 mL (120 mmol, 120eq) formaldehyde solution and 4.53 mL (120 mmol, 120 eq) formic acidwere added. The flask was equipped with a condenser and the reactionmixture was heated to 60° C. for 16 hour with an oil bath. After 16 hourthe mixture was allowed to cool to room temperature and the solventswere removed under reduced pressure. Then, the crude product wasdissolved in 20 mL EtOH anhydrous and 4 g of Amberlite resin was addedto the solution. The resulting mixture was stirred for 16 hour at roomtemperature before the resin was filtered of and the EtOH was removedunder reduced pressure. The resulting crude product was dissolved in 10mL CH₂Cl₂ and 10 mL of a 2 M aqueous solution of NaOH in water. Thephases were separated and the aqueous layer was extracted three timeswith 10 mL of CH₂Cl₂. The organic phases were dried over MgSO₄ and theCH₂Cl₂ was removed under reduced pressure to yield the methylatedpolyethyleneimine as a yellow oil.

Methylated polyethyleneimine (M.W. 600 before methylation):

¹H NMR (CDCl₃, 400 MHz): δ=2.18-2.91 (m), no NH signal appear in thespectra

¹³C NMR (CDCl₃, 100.7 MHz): δ=42.2 (q), 44.1 (q), 44.4 (q), 50.5-56.0(m, t)

Methylated polyethyleneimine (M.W. 1800 before methylation)

¹H NMR (CDCl₃, 400 MHz): δ=2.16 (s, CH₃), 2.23 (bs, CH₃), 2.44-2.64 (m),no NH signal appear in the spectra

¹³C NMR (CDCl₃, 100.7 MHz): δ=41.5 (q), 44.0 (q), 50.8-51.1 (m, t), 53.7(t), 55.0 (t)

Methylated polyethyleneimine (M.W. 1800 before methylation)

¹H NMR (CDCl₃, 400 MHz): δ=2.18 (s, CH₃), 2.21 (s, CH₃), 2.28-2.62 (m),no NH signal appear in the spectra.

¹³C NMR (CDCl₃, 100.7 MHz): δ=42.9 (q), 43.0 (q), 45.9 (q), 46.0 (q),52.8-54.0 (m, t), 55.8-56.9 (m, t), 57.2-57.8 (m, t)

Example 16B Use of the Polyamine to Expel Acetonitrile from Water

The methylated polyamines were investigated as additives for switchableionic strength solutions. To measure the extent of acetonitrile beingforced out of an aqueous phase by an increase in ionic strength, and theamounts of amine, which remained in the aqueous phase, 1:1 w/w solutionsof acetonitrile and water (1.5 g each) were prepared in graduatedcylinders. 300 mg of the non-ionic polyamine additive were added and thecylinders were capped with rubber septa. After 30 min of bubbling carbondioxide through the liquid phase from a single narrow gauge steel needleat room temperature, a visible phase separation was observed. Thevolumes of each phase were recorded. Aliquots of the non-aqueous andaqueous layers were taken and dissolved in D₂O in NMR tubes. A knownamount of ethyl acetate or dimethylformamide (DMF) was added to each NMRtube as an internal standard. ¹H NMR spectra were acquired and throughintegration of the ethyl acetate or DMF standard, a concentration ofacetonitrile or additive was calculated and scaled up to reflect thetotal volume of the aqueous or non-aqueous phase giving a percentage ofthe compound being forced out. The results are shown in the followingtable.

polyethyleneimine Acetonitrile forced out M.W. 600 56% M.W. 1800 72%M.W. 10000 77%

99.9% of the polyamine was retained in the aqueous phase.

Argon was then bubbled through the solution while heating to 50° C.until the two phases recombined into a single phase (typically 30 min).Bubbling CO₂ through the mixture again for 30 min caused the liquidmixture to split into two phases and a subsequent bubbling of argon for30 min caused the two phases to merge again, which shows that theprocess was fully reversible.

Example 17 Preparation and Use of a Tetraamine for Expulsion of THF fromWater Example 17A Preparation of the Tetraamine

Spermine (97% purity) was purchased from Alfa Aesar, formaldehyde (37%in H₂O), Zn powder from Sigma-Aldrich and acetic acid from FisherScientific.

A 250 mL round bottom flask was equipped with a 2 cm teflon stirring barand placed over a magnetic stirring plate. 2.02 g (10 mmol, 1.0 eq)spermine were placed in the flask and dissolved in 40 mL water.Afterwards, 9.72 mL (120 mmol, 12.0 eq) formaldehyde solution and 13.7mL (240 mmol, 24.0 eq) acetic acid were added and the solution wasallowed to stir at room temperature for 15 min. Afterwards, 7.84 g (120mmol, 12.0 eq) Zn powder were added in small portions, which resulted ingas formation. A cold water bath was used to maintain the temperature inthe flask under 40° C. After complete addition the reaction mixture wasvigorously stirred for 16 hour at room temperature. 20 mL NH₃-solutionwere added and the aqueous phase was extracted with ethyl acetate in aseparation funnel (3×25 mL).

The combined organic layers were dried over MgSO₄, filtered throughfilter paper removed under reduced pressure. The crude product waspurified by high vacuum distillation to yield 1.3 g (4.5 mmol, 42%) of ayellow oil which was formally calledN¹,N^(1′)-(butane-1,4-diyl)bis(N¹,N³,N³-trimethylpropane-1,3-diamine).As used herein, this compound is referred to as MeSpe (i.e. methylatedspermine).

¹H NMR (CDCl₃, 400 MHz): δ=1.36-1.44 (m, 4H, CH₂), 1.55-1.66 (m, 4H,CH₂), 2.18 (s, 6H, CH₃), 2.19 (s, 12H, CH₃), 2.21-2.27 (m, 4H, CH₂),2.28-2.35 (m, 8H, CH₂);

¹³C NMR (CDCl₃, 100.7 MHz): δ=25.3 (t), 25.7 (t), 42.3 (q), 45.6 (q),55.8 (t), 57.8 (t), 58.0 (t);

MS (EI): m/z (%)=287.32 (7), 286.31 (41) [M]⁺, 98.08 (28), 86.08 (44),85.07 (100), 84.07 (41);

HRMS (EI): calc. for [M]⁺: 286.3097, found: 286.3091.

Example 17B Reversible Solvent Switching of Tetraamine/Water System

The methylated spermine was investigated as an additive for switchableionic strength solutions. To measure the extent of THF being forced outof an aqueous phase by an increase in ionic strength, and the amounts ofamine, which remained in the aqueous phase, 1:1 w/w solutions of THF andwater were prepared in graduated cylinders. The appropriate mass ofamine additive to result in a 0.80 molal solution was added and thecylinders were capped with rubber septa. After 30 minutes of bubblingcarbon dioxide through the liquid phase from a single narrow gauge steelneedle, a visible phase separation was observed. The volumes of eachphase were recorded. Aliquots of the non-aqueous and aqueous layers weretaken and dissolved in d₃-acetonitrile in NMR tubes. A known amount ofethyl acetate was added to each NMR tube as an internal standard. ¹H NMRspectra were acquired and through integration of the ethyl acetatestandard, a concentration of THF or additive was calculated and scaledup to reflect the total volume of the aqueous or non-aqueous phasegiving a percentage of the compound being forced out or retained. Thenargon was bubbled through the solution while heating to 50° C. until thetwo phases recombined (15 to 60 min). The whole switching process (30min CO₂, sample take, then another 30 min of Ar) was repeated. Theresults are shown in the following table.

Salting Out-Experiments Using Methylated Spermine (MeSpe).

run THF forced out Additive retained in THF 1 84.3% 99.85% 2 85.5%99.79%

Example 17C NMR Measurement of the Degree of Protonation of MethylatedSpermine by Carbonated Water

The degree of protonation of the tetraamine (methylated spermine) uponcontact with a carbon dioxide trigger was investigated by ¹H NMR.

In order to establish the chemical shifts of the protonated bases, molarequivalents of several strong acids, including HCl and HNO₃, were addedto separate solutions of the tetraamine dissolved in D₂O. ¹H NMR spectrawere acquired on a Bruker AV-400 NMR spectrometer at 400.3 MHz for threereplicate solutions of the amine. An average value of each chemicalshift for each protonated base was calculated along with standarddeviations. If the base when reacted with the trigger to ionic salt formshowed chemical shifts within this error range, it was considered to be100% protonated within experimental error. The ¹H NMR chemical shifts ofthe unprotonated amine were also measured.

The extent of protonation of the additive at room temperature at 0.1 M(in D₂O) was monitored by ¹H NMR. The amine was dissolved in D₂O in anNMR tube and sealed with a rubber septa. The spectrum was then acquired.Subsequently, two narrow gauge steel needles were inserted and gas wasgently bubbled through one of them into the solution at approximately4-5 bubbles per second. The second needle served as a vent for thegaseous phase.

Firstly CO₂ was bubbled through the solution for the required length oftime and then the spectrum was re-acquired. This process was repeated.The % protonation of the amine was determined from the observed chemicalshifts by determining the amount of movement of the peaks from thenormal position for the unprotonated amine towards the position expectedfor the fully protonated amine.

The results show that the tetramine was protonated to a degree of 93%.

Example 18 Osmotic Desalination System

Water desalination by reverse osmosis is energetically costly. Analternative that has been proposed in the literature is forward osmosis(FIG. 18), where water flows across a membrane from seawater into aconcentrated ammonium carbonate solution (the “draw solution”). Once theflow is complete, the draw solution is removed from the system andheated to eliminate the NH₃ and CO₂. The principle costs of the processare the energy input during the heating step and the supply of make-upammonium carbonate. The limiting factors for the technology are,according to a 2006 review of the field (Cath, T. Y.; Childress, A. E.;Elimelech, M. J. Membrane Sci. 2006, 281, 70-87). a “lack ofhigh-performance membranes and the necessity for an easily separabledraw solution.”

Described in this example is a new easily separable draw solution, whichtakes advantage of the present method of reversibly converting aswitchable water from low to high ionic strength. The osmotic pressureof a switchable water should dramatically rise as the conversion fromlow ionic strength to high ionic strength takes place. Although theosmotic pressures of the solution before and after CO₂ have not beenmeasured, literature data (Cath, T. Y.; Childress, A. E.; Elimelech, M.J. Membrane Sci. 2006, 281, 70-87) show that the osmotic pressure of a 4M solution of a neutral organic such as sucrose is much lower (about 130atm) than the osmotic pressure of a salt containing a dication such asMgCl₂ (800 atm). This reversible change in osmotic pressure can be usedin a method for desalination of water as depicted in FIG. 19.

The process depicted in FIG. 19 employs a switchable water solution inits ionic form as the draw solution. After forward osmosis, the seawateris removed and the CO₂ is removed from the switchable water solution,dropping the osmotic pressure dramatically. Reverse osmosis producesfresh water from the switchable water solution with little energyrequirement because of the low osmotic pressure.

The key advantages of this process over conventional forward osmosis arethe expected lower energy requirement for the heating step (see Table ofexpected energy requirements below) and the facile and completerecycling of the amine. The key advantage of the proposed process overconventional reverse osmosis is the much lower pressure requirementduring the reverse osmosis step.

Energy requirement Energy requirement for process with for proposedProcess step NH₄CO₃, kJ/mol process, kJ/mol Deprotonation of NH₄ ⁺ or52.3³ 36.9³ NR₃H⁺ Removal of CO₂ from 19.4 19.4 water Removal of NH₃from 30.5 0 water Reverse osmosis step 0 unknown TOTAL 102.2 >56.3³Mucci, A.; Domain, R.; Benoit, R. L. Can. J. Chem. 1980, 58, 953-958.

A modification of this process, shown in FIG. 20, differs only in thelast step, where the switchable water additive in the solution isswitched “off”, or back to its nonionic form, and then removed by amethod other than reverse osmosis. For example, if the non-ionic form ofthe additive is insoluble or immiscible with water, then it can beremoved by filtration or decantation, with any small amounts ofremaining additive in the water being removed by passing the waterthrough silica. Results have shown successful use of such a separationprocess.

Sodium chloride was purchased from EMD Chemicals (Gibbstown, N.J., USA)while bone dry grade carbon dioxide was purchased from Air Liquide(Toronto, ON, Canada). The Seapack Emergency Desalinator bag waspurchased from Hydration Technology Innovations (Scottsdale, Ariz.,USA). Ultra pure water (18 MΩ) was obtained using an Elga Lab WaterPureLab Flex system (High Wycombe, UK). Reverse Osmosis (RO) experimentswere conducted using a Sterlitech HP4750 Stirred cell with two differentSterlitech ultra filtration membranes (TF UF GM membrane PN: YMGMSP3301and Koch Flat sheet membrane HFK 131 PN: YMHFK13118).

Example 18A Forward and Reverse Osmosis Experiments with 1% Salt WaterUsing MW=35 k Functionalized PMMA

A solution of 15 g of 3-(dimethylamino)-1-propylamine functionalizedpolymethyl methacrylate (MW=35,000) in 85 mL deionized water was addedto the inner membrane nutrient delivery spout (green capped) of thedesalination bag. Carbon dioxide was introduced to the same solutiondirectly in the bag via a glass dispersion tube at a pressure of 10 psi.Bubbling was continued for 45 minutes. A solution of 1 weight % sodiumchloride in water (1050 mL) was added to the sample port (red capped) ofthe desalination bag typically used for introduction of seawater. Thebag was left at room temperature for 6 hours and then the polymersolution was poured out via the green capped spout. The volume ofsolution was approximately 145 mL and the solution was returned to thebag via the same spout. An additional 15 g of solid polymer was addedvia the same spout along with an additional 15 mL of water. The bag wasagitated for approximately 10 minutes by hand and then carbon dioxidewas bubbled through polymer solution for 1 hour and rinsed with anadditional 15 mL of water. The bag was left for 16 hours at roomtemperature followed by measuring the volume of polymer solution whichwas found to be approximately 370 mL. The solution was then heated to75° C. for 5 hours in a glass media jar until no evolution of gasbubbles was observed indicating solution was “switched off”.

The stirred cell was equipped with a membrane and 100 mL of the3-(dimethylamino)-1-propylamine functionalized PMMA aqueous solution wasadded. The cell was closed and pressurized with argon. The table showsthe use of two different membranes and pressures and flux needed foreach experiments.

Polymer solution Membrane Pressure Flux (ml/min) PMMA 35,000 TF UF GM 67bar 0.167 PMMA 35,000 HFK 131 40 bar 0.075

Example 18B Forward and Reverse Osmosis Experiments with 1% Salt WaterUsing MW=15 k Functionalized PMMA

A solution of 15 g of 3-(dimethylamino)-1-propylamine functionalizedpolymethyl methacrylate (MW=15,000) in 100 mL deionized water was addedto the inner membrane nutrient delivery spout (green capped) of thedesalination bag. A solution of 1 weight % sodium chloride in water(1050 mL) was added to the sample port (red capped) of the desalinationbag typically used for introduction of seawater. The bag was left atroom temperature overnight without carbonating and then the polymersolution was poured out via the green capped spout. The volume of thesolution was approximately 115 mL, which was unchanged since the polymersolution was not “switched on” by carbon dioxide. The solution wasreturned to the bag via the same spout and carbonated directly bybubbling with carbon dioxide using gas dispersion tube at 10 psi for 45minutes. The bag was left for 16 hours at room temperature followed bymeasuring the volume of polymer solution which was found to beapproximately 250 mL. This solution was again carbonated directly bybubbling with carbon dioxide using a gas dispersion tube at 10 psi for 5minutes, and 100 mL of it was set aside for reverse osmosis experimentin “switched on” form. Remaining solution was heated to 70° C. for 2hours in a glass media jar until no evolution of gas bubbles wasobserved indicating solution was “switched off”.

Reverse Osmosis in Switched On Form

The stirred cell was equipped with a membrane and above 100 mL of3-(dimethylamino)-1-propylamine functionalized PMMA aqueous solution wasadded without previously removing the CO₂. The cell was closed andpressurized with argon. The table shows the use of two differentmembranes and pressures and flux needed for each experiment.

Polymer solution Membrane Pressure Flux (ml/min) PMMA 15,000 (“ON”) TFUF GM 40 bar 0.30 PMMA 15,000 (“ON”) HFK 131 40 bar 0.20

Reverse Osmosis in Switched Off Form

The stirred cell was equipped with a membrane and 100 mL of3-(dimethylamino)-1-propylamine functionalized PMMA aqueous solution wasadded in the deactivated form. The cell was closed and pressurized withargon. The table shows the use of two different membranes and pressuresand flux needed for each experiment.

Polymer solution Membrane Pressure Flux (ml/min) PMMA 15,000 (“OFF”) TFUF GM 40 bar 0.20 PMMA 15,000 (“OFF”) HFK 131 40 bar 0.28

Forward Osmosis using DMCA as Draw Solution

A draw solution of 127.0 mL (108.0 g, 0.85 mol) dimethylcyclohexylaminein 127.0 mL deionized water was prepared. It was carbonated by bubblingwith carbon dioxide using a gas dispersion tube at 1 atm for 1.5 h untilall of the amine disappeared and added to the inner membrane nutrientdelivery spout (green capped) of the desalination bag. A solution of 1weight % sodium chloride in water (1.0 L) was added to the sample port(red capped) of the desalination bag typically used for introduction ofseawater. After 5 h the draw solution was removed from the pack and thevolume measured (900 mL), while the volume of the NaCl feeding solutiondecreased to 350 mL. Due to the low concentration of DMCA in water andincomplete conversion of the salt, it was not possible to force the DMCAout of the water.

Example 19 Preparation and Use of a Diamidine for Expulsion of THF fromWater Example 19A Preparation of the Diamidine

1,4-Diaminobutane was purchased from Sigma-Aldrich and dimethylacetamidedimethylacetale was purchased from TCI.

A 100 mL flask was equipped with a condenser and a 1 cm stirring bar andwas then placed over a stirplate. 1.14 mL (1.0 g, 11.3 mmol, 1 eq.) of1,4-diaminobutane and 3.64 mL (3.31 g, 24.9 mmol, 2.2 eq.) ofdimethylacetamide dimethylacetate were the placed into the flask. Thereaction mixture was then stirred with 600 rpm and heated to 60° C.After 2 h the reaction mixture was allowed to cool to room temperatureand the resulting methanol was removed under reduced pressure to yield ayellow oil. This crude product was then purified by high vacuumdistillation. The pure product was obtained as a light yellow oil (2.32g, 10.2 mmol, 91%). The compound was calledN′,N″-(butane-1,4-diyl)bis(N,N-dimethylacetimidamide) and in thisapplication is referred to as “DIAC” (i.e. diacetamidine)

¹H NMR (CDCl₃, 400 MHz): δ=1.45-1.53 (m, 4H, CH₂), 1.80 (s, 3H, CON,2.79 (s, 6H, N(CH₃)₂), 3.09-3.19 (m, 4H, CH₂);

¹³C NMR (CDCl₃, 100.7 MHz): δ=12.3 (q, CCH₃), 30.2 (t, CH₂), 37.9 (q,2C, N(CH₃)₂), 50.0 (t, CH₂), 158.7 (s);

MS (EI): m/z (%)=227.22 (3), 226.21 (21), 198.16 (7), 182.17 (7), 141.14(14), 140.13 (21), 128.11 (10), 127.10 (30), 114.11 (23), 113.11 (28),112.09 (52), 99.09 (27), 70.07 (45), 56.05 (100);

HRMS (EI): calc. for [M]⁺: 226.2157, found: 226.2161.

Example 19B Reversible Solvent Switching of Diamidine/Water System

The diamidine was investigated as additive for switchable ionic strengthsolutions. To measure the extent of THF being forced out of an aqueousphase by an increase in ionic strength, and the amounts of amine, whichremained in the aqueous phase, 1:1 w/w solutions of THF and water wereprepared in graduated cylinders. The appropriate mass of amine additiveto result in a 0.80 molal solution was added and the cylinders werecapped with rubber septa. After 30 minutes of bubbling carbon dioxidethrough the liquid phase from a single narrow gauge steel needle, avisible phase separation was observed. The volumes of each phase wererecorded. Aliquots of the non-aqueous and aqueous layers were taken anddissolved in d₃-acetonitrile in NMR tubes. A known amount of ethylacetate was added to each NMR tube as an internal standard. ¹H NMRspectra were acquired and through integration of the ethyl acetatestandard, a concentration of THF or additive was calculated and scaledup to reflect the total volume of the aqueous or non-aqueous phasegiving a percentage of the compound being forced out or retained. Theresults showed that the amount of THF forced out of the aqueous phasewas 54.5% and the amount of additive retained in the aqueous phase was99.5%

Then argon was bubbled through the solution while heating to 50° C.until the two phases recombined (15 to 60 min).

Example 20 Precipitation of an Organic Solid Using Switchable Water

Ten millilitres of water was pipetted into a glass centrifuge tube alongwith 2.038 g TMDAB (˜5:1 w/w solution). 68.2 mg of (+)-camphor (used asis from Sigma-Aldrich) was added to the solution. The solution washeated in a 70° C. water bath to expedite the dissolution of thecamphor. After complete dissolution of the solid (camphor) and coolingto room temperature (23° C.), the solid remained dissolved in theaqueous solution.

The centrifuge tube was capped with a rubber septum. CO₂ was introducedinto the solution via a single narrow gauge steel needle at a flow rateof about 5 mL min⁻¹. A second needle was inserted into the tube, but notinto the solution, to act as a gas outlet. After 30 minutes of bubblingCO₂ through the solution a white precipitate appeared throughout theaqueous solution.

The solution was centrifuged for 5 minutes, using a Fisher ScientificCentrific 228 centrifuge at a speed of 3300 RPM, such that all the whitesolids collected at the top of the aqueous solution. The white solidswere collected by vacuum filtration and weighed on a Mettler-ToledoAG245 analytical balance. A mass of 24.0 mg was obtained, resulting in a35.2% recovery of the original dissolved solid.

Example 21 Primary Amines as Switchable Additives

Primary amines were tested as switchable water additives. The switchingof the non-ionized form to the charged form (which is probably a mixtureof bicarbonate and carbamate salts) proceeded well. The separation of anorganic liquid was observed. However, conversion of the ionic form backto the non-ionized form was unsuccessful. Primary amines are thereforeonly useful as additives in applications where a single switch to theionic form, without conversion back to the non-ionized form, issufficient. Thus, primary amine additives are not reversibly“switchable”.

Example 21A Ethanolamine (5:5:1)

In a glass vial, 5.018 g H₂O, 1.006 g ethanolamine, and 4.998 g THF weremixed to generate a single phase, clear, colourless solution. A stir barwas added to the vial and the vial was capped with a rubber septa. CO₂was introduced into the solution via a single narrow gauge steel needleat a flow rate of about 5 mL min⁻¹. A second needle was inserted throughthe septa, but not into the solution, to act as a gas outlet. CO₂ wasbubbled through the solution for 20 minutes until two liquid phases(aqueous and organic) were observed. It was found by ¹H NMR spectroscopythat ˜62% of the THF was forced out of the aqueous phase into the neworganic phase.

The two phase mixture was then placed in a 60° C. water bath while N₂was bubbled through the mixture in a fashion similar to the previousbubbling of CO₂. This was performed for 60 minutes. Although some THFboiled off, the two phases did not recombine. The temperature wasincreased to 75° C. for 30 minutes which appeared to boil off theremainder of the THF as the volume returned to that of the water andamine mixture. Some ethanolamine may have boiled off as well. At thispoint, a single liquid phase was observed, as the THF was boiled off,however, the phase was cloudy and it appeared to have a whiteprecipitate (likely carbamate salts).

The temperature of the water bath was then increased to 85° C. and N₂bubbling was continued for 90 minutes, giving a total N₂ treatment of 3hours. No additional physical changes were observed. The solutionremained cloudy white in colour and some of the white precipitate hadcollected on the sides of the vial.

Example 21B Ethylenediamine (18:18:1)

In a glass vial, 5.004 g H₂O, 0.283 g ethylenediamine, and 5.033 g THFwere mixed to generate a single phase, clear, colourless solution. Astir bar was added to the vial and the vial was capped with a rubbersepta. CO₂ was introduced into the solution via a single narrow gaugesteel needle at a flow rate of about 5 mL min⁻¹. A second needle wasinserted through the septa, but not into the solution, to act as a gasoutlet. CO₂ was bubbled through the solution for 10 minutes until twoliquid phases (aqueous and organic) were observed. It was found by ¹HNMR that ˜67% of the THF was forced out of the aqueous phase into thenew organic phase.

The two phase mixture was then placed in a 60° C. water bath while N₂was bubbled through the mixture in a fashion similar to the previousbubbling of CO₂. This was performed for 60 minutes where some THFevaporated, but the two phases did not recombine. The temperature of thewater bath was then increased to 85° C. and N₂ bubbling was continuedfor 120 minutes, giving a total N₂ treatment of 3 hours. It appearedthat all of the THF had evaporated as the volume had returned to that ofthe water and amine mixture. The solution was a single yellow liquidphase at this point, however a white precipitate (likely carbamatesalts) caused the solution to appear cloudy.

Example 22 Salting out THF from Water using Secondary Amine SwitchableAdditives

In general, from the observations using primary amines, secondary amineswere expected to be difficult to reverse, because both secondary andprimary amines tend to form carbamate salts in addition to bicarbonatesalts when their aqueous solutions are contacted with CO₂. However thefollowing secondary amines were found to be reversibly switchable.Without wishing to be bound by theory, it is possible that thereversibility results from a tendency to form more bicarbonate thancarbamate salts.

The N-tert-butylethanolamine was purchased from TCI America andN-tert-butymethylamine was purchased from Sigma-Aldrich. Both compoundswere used without further purification.

N-tert-Butylethanolamine and N-tert-butymethylamine were investigated asadditives for switchable ionic strength solutions. To measure the extentof THF being forced out of an aqueous phase by an increase in ionicstrength, and to measure the amount of amine remaining in the aqueousphase, 1:1 w/w solutions of THF and water (1.5 g each) were prepared ingraduated cylinders. The appropriate mass of amine additive to result ina 1.60 molal solution was added and the cylinders were capped withrubber septa. After 30 minutes of bubbling carbon dioxide through theliquid phase from a single narrow gauge steel needle, a visible phaseseparation was observed. The volumes of each phase were recorded.Aliquots of the non-aqueous and aqueous layers were taken and dissolvedin d₃-acetonitrile in NMR tubes. A known amount of ethyl acetate wasadded to each NMR tube as an internal standard. ¹H NMR spectra wereacquired and through integration of the ethyl acetate standard, aconcentration of THF or additive was calculated and scaled up to reflectthe total volume of the aqueous or non-aqueous phase giving a percentageof the compound being forced out or retained. Then argon was bubbledthrough the solution at 5 mL/min while heating to 50° C. until the twophases recombined (30 min for N-tert-butylethanolamine). The recombiningof the phases when N-tert-butylmethylamine was used as an additive wasnot successful at 30 min but was achieved after 2 hours at a higher Arflow rate of 15 mL/min. THF was added afterwards to replace the amountof THF being evaporated during the procedure. The whole switchingprocess (30 min CO₂, sample take, then another Ar treatment) wasrepeated. The results are shown in the following table.

Salting Out-Experiments Using Secondary Amine Additives.

Amine THF forced out Additive retained in H2O N-tert-butylethanolamine68.7 ± 0.4% 99.84 ± 0.04% N-tert-butymethylamine 67.6 ± 0.8% 99.75 ±0.04%

Example 23 Synthesis of Polymeric Switchable Water Additives

Polyethyleneimines (“PEIs”, MW=600, 99%; 1,800, 99%; 10,000, 99%) werepurchased from Alfa Aesar. Iodoethane, 99%, Iodopropane, 99% Iodobutane,99% and K₂CO₃ were purchased from Sigma-Aldrich. NaOH was purchased fromAcros. EtOH was purchased from Greenfield Alcohols. Ethyl acetate andMgSO₄ were purchased from Fisher. All reagents were used without furtherpurification. A 15% (w/v) NaOH solution was made by dissolving 15 g ofNaOH in 100 mL deionized water.

General procedure I (GP I) for the alkylation of PEIs: In a round bottomflask, equipped with a magnetic stir-bar, iodoalkane was dissolved inabsolute EtOH and stirred at 600 rpm. To this, a solution of PEI in EtOHand solid K₂CO₃ were added. The round bottom flask was then equippedwith a reflux condenser and the reaction mixture was heated to reflux(80° C.) for 3 days. After cooling to room temperature, the K₂CO₃ wasfiltered off and the EtOH was removed under reduced pressure. The crudeproduct was then dissolved in a mixture of EtOAc and 15% (w/v) NaOHsolution in water. The phases were separated and the organic layer waswashed twice with 15% (w/v) NaOH solution in water. The organic layerwas then dried with MgSO₄ and removed under reduced pressure to yieldyellow oils.

General procedure II (GP II) for the alkylation of PEIs: In a roundbottom flask, equipped with a magnetic stir-bar, iodoalkane wasdissolved in absolute EtOH and stirred at 600 rpm. To this, a solutionof PEI in EtOH and solid K₂CO₃ were added. The round bottom flask wasthen equipped with a reflux condenser and the reaction mixture washeated to reflux (80° C.) for 3 days. After cooling to room temperature,another portion of K₂CO₃ was added and the mixture was refluxed againfor 3 d. After cooling to r.t., the K₂CO₃ was filtered off and the EtOHwas removed under reduced pressure. The crude product was then dissolvedin a mixture of EtOAc and 15% (w/v) NaOH solution in water. The phaseswere separated and the organic layer was washed twice with 15% (w/v)NaOH solution in water. The organic layer was then dried with MgSO₄ andremoved under reduced pressure to yield yellow oils.

23.1.1 Synthesis of Ethylated Polyethyleneimines (EPEI)

23.1.1.1 Ethylated Polyethyleneimine (EPEI) MW=600

According to GP I, 3.1 mL (6.1 g, 39.0 mmol) iodoethane in 10 mL EtOHwas reacted with 1.8 g (41.9 mmol) polyethyleneimine (MW=600) in 10 mLEtOH in the presence of 8.3 g (60.0 mmol) K₂CO₃. Work-up with NaOH (3×10mL) and EtOAc (10 mL) yielded 1.84 g (65%) of a light yellow oil.

¹H NMR (CDCl₃, 400 MHz): δ=0.969 (bt, 3H, CH₃), 2.39-2.56 (m, 6H, CH₂);

¹³C NMR (CDCl₃, 100.7 MHz): δ=11.8 (CH₃), 47.4 (CH₂ ethyl), 48.6 (CH₂ethylene), 50.9-54.0 (CH₂ ethylene);

NMR spectrum shows 9% quaternized nitrogens in the polymer.

IR (film): {tilde over (υ)} [cm⁻¹]=2967 (s), 2934 (m), 2808 (s), 1653(w), 1457 (m), 1382 (w), 1292 (w), 1097 (w), 1062 (m).

23.1.1.2 Ethylated Polyethyleneimine (EPEI) MW=1,800

According to GP I, 3.1 mL (6.1 g, 39.0 mmol) iodoethane in 10 mL EtOHwas reacted with 1.8 g (41.9 mmol) polyethyleneimine (MW=1,800) in 10 mLEtOH in the presence of 8.3 g (60.0 mmol) K₂CO₃. Work-up with NaOH (3×10mL) and EtOAc (10 mL) yielded 2.38 g (84%) of a light brown oil.

¹H NMR (CDCl₃, 400 MHz): δ=0.91 (bt, 3H, CH₃), 2.38-2.54 (m, 6H, CH₂);

¹³C NMR (CDCl₃, 100.7 MHz): δ=11.8 (CH₃), 47.5 (CH₂ ethyl), 50.8-54.1(CH₂ backbone);

IR (film): {tilde over (υ)} [cm⁻¹]=2966 (s), 2933 (m), 2807 (s), 1456(m), 1382 (w), 1292 (w), 1097 (w), 1061 (m).

23.1.1.3 Ethylated Polyethyleneimine (EPEI) MW=10,000

According to GP I, 3.1 mL (6.1 g, 39.0 mmol) iodoethane in 10 mL EtOHwas reacted with 1.8 g (41.9 mmol) polyethyleneimine (MW=10,000) in 10mL EtOH in the presence of 8.3 g (60.0 mmol) K₂CO₃. Work-up with NaOH(3×10 mL) and EtOAc (10 mL) yielded 2.23 g (78%) of a light yellow oil.

¹H NMR (CDCl₃, 400 MHz): δ=0.98 (bt, 3H, CH₃), 1.40 (bs, remaining freeNH), 2.42-2.62 (m, 6H, CH₂);

NMR spectrum shows 7% quaternized nitrogens in the polymer.

¹³C NMR (CDCl₃, 100.7 MHz): δ=11.7 (CH₃), 47.4 (CH₂ ethyl), 47.8-54.0(CH₂ backbone);

IR (film): {tilde over (υ)} [cm⁻¹]=2973 (s), 2809 (s), 1643 (w), 1562(w), 1471 (m), 1100 (w), 1055 (w).

23.1.2 Synthesis of Propylated Polyethyleneimines (PPEI)

23.1.2.1 Propylated Polyethyleneimine (PPEI) MW=600

According to GP II, 4.7 mL (8.2 g, 48.0 mmol) iodopropane in 10 mL EtOHwas reacted with 1.8 g (41.9 mmol) polyethyleneimine (MW=600) in 10 mLEtOH in the presence of 21.6 g (156.0 mmol) K₂CO₃ (over two equaladditions). Work-up with NaOH (3×10 mL) and EtOAc (10 mL) yielded 2.54 g(71%) of a yellow oil.

¹H NMR (CDCl₃, 400 MHz): δ=0.84 (bt, 3H, CH₃), 1.41 (bq, 2H, CH₂,propyl), 2.30-2.39 (m, 2H, CH₂, propyl), 2.43-2.57 (m, 4H, CH₂,backbone);

NMR spectrum shows 6% quaternized nitrogens in the polymer.

¹³C NMR (CDCl₃, 100.7 MHz): δ=11.4 (CH₃), 20.4 (CH₂, propyl), 52.2-53.9(CH₂ backbone) 56.9 (CH₂, propyl);

IR (film): {tilde over (υ)} [cm⁻¹]=2957 (s), 2933 (m), 2807 (s), 1458(m), 1378 (w), 1261 (w), 1076 (w), 800 (m).

23.1.2.2 Propylated Polyethyleneimine (PPEI) MW=1,800

According to GP II, 4.7 mL (8.2 g, 48.0 mmol) iodopropane in 10 mL EtOHwas reacted with 1.8 g (41.9 mmol) polyethyleneimine (MW=1,800) in 10 mLEtOH in the presence of 21.6 g (156.0 mmol) K₂CO₃ (over two equaladditions). Work-up with NaOH (3×10 mL) and EtOAc (10 mL) yielded 2.3 g(65%) of a yellow oil.

¹H NMR (CDCl₃, 400 MHz): δ=0.83 (bt, 3H, CH₃), 1.41 (bq, 2H, CH₂,propyl), 1.76 (bs, remaining free NH), 2.35 (bq, 2H, CH₂, propyl),2.42-2.58 (m, 4H, CH₂, backbone);

NMR spectrum shows 12% quaternized nitrogens in the polymer.

¹³C NMR (CDCl₃, 100.7 MHz): δ=12.1 (CH₃), 20.3 (CH₂, propyl), 52.3-53.9(CH₂ backbone) 56.8 (CH₂, propyl);

IR (film): {tilde over (υ)} [cm⁻¹]=3421 (s), 2958 (s), 2872 (m), 2809(s), 1653 (m), 2559 (m), 1464 (m), 1379 (w), 1076 (w), 800 (m).

23.1.2.3 Propylated Polyethyleneimine (PPEI) MW=10,000

According to GP II, 5.7 mL (10.0 g, 5870 mmol) iodopropane in 12 mL EtOHwas reacted with 1.8 g (41.9 mmol) polyethyleneimine (MW=10,000) in 12mL EtOH in the presence of 26.2 g (190.0 mmol) K₂CO₃ (over two equaladditions). Work-up with NaOH (3×12 mL) and EtOAc (12 mL) yielded 4.2 g(99%) of a yellow oil.

¹H NMR (CDCl₃, 400 MHz): δ=0.82 (bt, 3H, CH₃), 1.40 (bq, 2H, CH₂,propyl), 1.76 (bs, remaining free NH), 2.34 (bq, 2H, CH₂, propyl),2.42-2.58 (m, 4H, CH₂, backbone);

NMR spectrum shows 15% quaternized nitrogens in the polymer.

¹³C NMR (CDCl₃, 100.7 MHz): δ=11.8 (CH₃), 20.4 (CH₂, propyl), 52.2-53.9(CH₂ backbone) 56.8 (CH₂, propyl);

IR (film): {tilde over (υ)} [cm⁻¹]=3439 (m), 2958 (s), 2933 (m), 2872(s), 2808 (s), 1463 (m), 1379 (w), 1075 (w).

23.1.3 Synthesis of Butylated Polyethyleneimines (BPEI)

23.1.3.1 Butylated Polyethyleneimine (BPEI) MW=600

According to GP II, 5.46 mL (8.83 g, 48.0 mmol) iodobutane in 10 mL EtOHwas reacted with 1.8 g (41.9 mmol) polyethyleneimine (MW=600) in 10 mLEtOH in the presence of 21.6 g (156.0 mmol) K₂CO₃ (over two equaladditions). Work-up with NaOH (3×10 mL) and EtOAc (10 mL) yielded 3.95 g(98%) of a yellow oil.

¹H NMR (CDCl₃, 400 MHz): δ=0.86 (bt, 3H, CH₃), 1.19-1.30 (m, 2H, CH₂butyl), 1.31-1.42 (m, 2H, CH₂ butyl), 2.32-2.42 (m, 2H, CH₂ butyl),2.44-2.54 (m, CH₂ ethylene);

¹³C NMR (CDCl₃, 100.7 MHz): δ=14.1 (CH₃), 20.7 (CH₂ butyl), 29.4 (CH₂butyl), 52.4-54.1 (CH₂, ethylene) 54.5 (CH₂ butyl), 54.8-55.1 (CH₂ethylene);

IR (film): {tilde over (υ)} [cm⁻¹]=2956 (s), 2931 (s), 2861 (m), 2805(s), 1458 (m), 1376 (w), 1083 (m).

23.1.3.2 Butylated Polyethyleneimine (BPEI) MW=1,800

According to GP II, 5.46 mL (8.83 g, 48.0 mmol) iodobutane in 10 mL EtOHwas reacted with 1.8 g (41.9 mmol) polyethyleneimine (MW=1,800) in 10 mLEtOH in the presence of 21.6 g (156.0 mmol) K₂CO₃ (over two equaladditions). Work-up with NaOH (3×10 mL) and EtOAc (10 mL) yielded 2.50 g(62%) of a yellow oil.

¹H NMR (CDCl₃, 400 MHz): δ=0.86 (bt, 3H, CH₃), 1.24 (bq, 2H, CH₂ butyl),1.31-1.44 (m, 2H, CH₂ butyl), 1.64 (bs, remaining NH), 2.37 (q, 2H, CH₂butyl), 2.42-2.54 (m, CH₂ ethylene), NMR spectrum shows 14% quaternizednitrogens in the polymer;

¹³C NMR (CDCl₃, 100.7 MHz): δ=14.1 (CH₃), 20.7 (CH₂ butyl), 29.4 (CH₂butyl), 52.1-53.8 (CH₂, ethylene) 54.5 (CH₂ butyl), 58.0-59.2 (CH₂ethylene);

IR (film): {tilde over (υ)} [cm⁻¹]=3424, (s), 2957 (s), 2871 (m), 2810(s), 1647 (s), 1558 (w), 1458 (m).

23.1.3.3 Butylated Polyethyleneimine (BPEI) MW=10,000

According to GP II, 5.46 mL (8.83 g, 48.0 mmol) iodobutane in 10 mL EtOHwas reacted with 2.0 g (46.5 mmol) polyethyleneimine (MW=10,000) in 10mL EtOH in the presence of 21.2 g (154.0 mmol) K₂CO₃ (over two equaladditions). Work-up with NaOH (3×10 mL) and EtOAc (10 mL) yielded 2.47 g(55%) of a yellow oil.

¹H NMR (CDCl₃, 400 MHz): δ=0.88 (bt, 3H, CH₃), 1.27 (bq, 2H, CH₂ butyl),1.33-1.44 (m, 2H, CH₂ butyl), 2.32-2.43 (m, 2H, CH₂ butyl), 2.44-2.56(m, CH₂ ethylene);

NMR spectrum shows 3% quaternized nitrogens in the polymer.

¹³C NMR (CDCl₃, 100.7 MHz): δ=14.1 (CH₃), 20.7 (CH₂ butyl), 29.5 (CH₂butyl), 52.0-53.5 (CH₂, ethylene) 54.5 (CH₂ butyl), 54.8-55.1 (CH₂ethylene);

IR (film): {tilde over (υ)} [cm⁻¹]=2955 (s), 2930 (s), 2861 (m), 2805(s), 1467 (m), 1378 (w), 1080 (m).

23.2 Polydiallylmethylamine (MW=5,000)

Polydiallylmethylamine hydrochloride MW=5,000 (25% solids in water) waspurchased from Polysciences, Inc. NaOH was purchased from AcrosOrganics. Dichloromethane and MgSO₄ were purchased from Fisher. A 15%(w/v) solution was made by dissolving 15 g of NaOH in 100 mL deionizedwater.

4.0 g of Polydiallylmethylamine hydrochloride MW=5000 (25% solids inwater) was placed into a 50 mL round-bottom flask equipped with a 1 cmmagnetic stir-bar. 10 mL of dichloromethane was added and the mixturewas stirred at 600 rpm. Then 10 mL of 15% (w/v) NaOH solution was slowlyadded and the stirring was continued for 1 hour after complete addition.The mixture was then transferred into a 100 mL separation funnel and thephases were separated. The organic layer was then washed twice with 5 mLof a 15% (w/v) NaOH solution, dried over MgSO₄ and removed under reducedpressure. 0.5 g (69%) of the polydiallylmethylamine was obtained as ayellow solid.

23.3 Polymethyl Methacrylate (PMMA) Based Materials

All reactions were conducted in air unless stated otherwise. NMR spectrawere recorded on a Varian 400-MR NMR spectrometer (Agilent, Mississauga,Ontario, Canada). All NMR spectra are referenced against residualprotonated solvent.

All chemicals listed below were used as received. Polymethylmethacrylate (MW=15,000 and MW=35,000) was purchased from Acros Organics(Fisher Scientific, Ottawa, Ontario, Canada). Polymethyl methacrylate(MW=120,000), and 3-dimethylamino-1-propylamine were purchased from AlfaAesar (VWR, Mississauga, Ontario, Canada).

All solvents were used as received. Methanol was purchased from ACPChemicals (Montreal, Quebec, Canada). Isopropanol was purchased fromCalcdon Laboratories (Georgetown, Ontario, Canada). Tetrahydrofuran waspurchased from EMD Chemicals (Gibbstown, N.J., US).

3-(dimethylamino)-1-Propylamine Functionalized PMMA (IVIW=15,000):

Polymethyl methacrylate (1.47 g, 14.7 mmol) was weighed into a 100 mL 2neck round bottom flask with a stir bar and evacuated on vacuumline/refilled with nitrogen three times. A reflux condenser was also putunder inert atmosphere using same procedure.3-(dimethylamino)-1-propylamine (15 mL) was added via syringe to thepolymer and a reflux condenser was placed onto the flask. The mixturewas heated to 150° C. for 3 days under nitrogen. After this time, thereaction mixture was a clear and colourless solution and was allowed tocool to room temperature causing a white precipitate to form. The liquidwas decanted and the remaining solid was washed with 2-25 mL portions ofisopropanol. It was then dried at 80° C. under high vacuum for 5 hours.The solid was then broken up with a spatula until more of a powderformed and then re-dried using the same conditions for 16 hours. 1.02 gof white powder was obtained and approximately 80% of the methacrylatesites were functionalized, as determined by integration of theappropriate resonances in the ¹H NMR spectrum.

¹H NMR (400 MHz, D₂O) δ 3.64 (bs, 3H, OCH₃), 2.86 (t, J=8.0 Hz, 2H,NHCH₂), 2.58 (t, J=8.0 Hz, 2H, Me₂NCH₂), 2.35 (s, 6H, N(CH₃)₂), 2.0-1.6(b, 2H, backbone CH₂), 1.80 (m, 2H, CH₂CH₂CH₂), 1.2-0.7 (b, 3H, CH₃).

Large Scale Synthesis of 3-(Dimethylamino)-1-Propylamine FunctionalizedPMMA (MW=15,000):

Polymethyl methacrylate (40.0 g, 400 mmol) was weighed into a 1 L 2 neckround bottom flask with a stir bar and fitted with a condenser andrubber septum. The apparatus was evacuated on vacuum line/refilled withnitrogen three times. 3-(dimethylamino)-1-propylamine (350 mL) waspoured into the flask under a flow of nitrogen. The mixture was heatedto 150° C. for 4.5 days under nitrogen. After stirring overnight thereaction mixture was observed to be white and cloudy whereas after thefull reaction time it was more a clear and colourless solution and wasallowed to cool to room temperature. The condenser was removed under aflow of nitrogen and a distillation apparatus with condenser andreceiving flask was attached. The reaction flask was covered in aluminumfoil and the amine solvent distilled off under nitrogen atmosphere at155° C. for 2 hours followed by 165° C. for 1 hour before being allowedto cool. The clear solid was then dried at 90° C. under high vacuum for2 hours causing it to swell. The swollen solid was then broken up with aspatula and drying continued for 3 hours. It was then broken up with aspatula and drying continued for 2 hours. Grinding yielded a powderwhich was dried for 16 hours at 90° C. under high vacuum. 49.9 g oflight yellow powder was obtained and approximately 80% of themethacrylate sites were functionalized, as determined by integration ofthe appropriate resonances in the ¹H NMR spectrum.

¹H NMR (400 MHz, D₂O) δ 3.65 (bs, 3H, OCH₃), 2.89 (t, J=8.0 Hz, 2H,NHCH₂), 2.61 (t, J=8.0 Hz, 2H, Me₂NCH₂), 2.38 (s, 6H, N(CH₃)₂), 2.0-1.6(b, 2H, backbone CH₂), 1.82 (m, 2H, CH₂CH₂CH₂), 1.45-0.8 (b, 3H, CH₃).

23.3.1 3-(Dimethylamino)-1-Propylamine Functionalized PMMA (MW=35,000):

Polymethyl methacrylate (0.618 g, 6.17 mmol) was weighed into a 50 mL 2neck round bottom flask with a stir bar and evacuated on vacuumline/refilled with nitrogen three times. A reflux condenser was also putunder inert atmosphere using same procedure.3-(dimethylamino)-1-propylamine (4 mL) was added via syringe to thepolymer and a reflux condenser was placed onto the flask. The mixturewas heated to 150° C. for 16 hours under nitrogen. After this time, thereaction mixture was a light yellow liquid with yellow precipitate. Theliquid was decanted and the remaining light yellow solid was dried at80° C. under high vacuum for 2 hours. The solid was then broken up witha spatula until more of a powder formed and then re-dried using the sameconditions for another 2 hours. This step was repeated once more afterbreaking up brittle chunks of the polymer using a mortar and pestle togive a fine powder (in order to facilitate drying). 0.695 g of yellowpowder was obtained and approximately 50% of the methacrylate sites werefunctionalized, as determined by integration of the appropriateresonances in the ¹H NMR spectrum.

¹H NMR (400 MHz, D₂O) δ 3.64 (bs, 3H, OCH₃), 2.82 (t, J=8.0 Hz, 2H,NHCH₂), 2.53 (b, 2H, Me₂NCH₂), 2.31 (s, 6H, N(CH₃)₂), 2.0-1.6 (b, 2H,backbone CH₂), 1.76 (m, 2H, CH₂CH₂CH₂), 1.3-0.7 (b, 3H, CH₃).

Large Scale Synthesis of 3-(Dimethylamino)-1-Propylamine FunctionalizedPMMA (MW=35,000):

Polymethyl methacrylate (90.0 g, 899 mmol) was weighed into a 2 L 3 neckround bottom flask with a stir bar and fitted with a condenser, gasinlet and rubber septum. The apparatus was evacuated on vacuumline/refilled with nitrogen three times. 3-(dimethylamino)-1-propylamine(1 L) was poured into the flask under a flow of nitrogen. The mixturewas heated to 150° C. for 5 days under nitrogen. After reactingovernight the mixture was observed to be a white suspension withstirring hampered by the solid. It was allowed to cool to roomtemperature. The condenser was removed under a flow of nitrogen and adistillation apparatus with condenser and receiving flask was attached.The reaction flask was covered in aluminum foil and the amine solventdistilled off under nitrogen atmosphere at 155° C. followed by 160° C.then 165° C. for 6 hours before being allowed to cool. A ¹H NMR spectrumwas recorded of the distillate showing resonances correspondingprimarily to 3-(dimethylamino)-1-propylamine along with methanolbyproduct indicating successful reaction. ¹H NMR (400 MHz, CDCl₃) δ 3.28(s, 3H, CH₃OH), 2.63 (t, J=8.0 Hz, 2H, NHCH₂), 2.20 (b, 2H, Me₂NCH₂),2.11 (s, 6H, N(CH₃)₂), 1.50 (m, 2H, CH₂CH₂CH₂).

A small amount of residual liquid was decanted from the flask and thelight yellow crystalline solid was washed quickly with 100 mL ofisopropanol. It was then dried at 80° C. under high vacuum for 6 hourscausing it to swell. The swollen solid was then broken up with a spatulaand drying continued for 16 hours. Solid removed and ground yielding alight yellow powder which was added to a 1 L 2 neck round bottom flaskand dried for 16 hours at 80° C. under high vacuum. 101.8 g of lightyellow powder was obtained and approximately 80% of the methacrylatesites were functionalized, as determined by integration of theappropriate resonances in the ¹H NMR spectrum.

¹H NMR (400 MHz, D₂O) δ 3.64 (bs, 3H, OCH₃), 2.87 (t, J=8.0 Hz, 2H,NHCH₂), 2.59 (t, J=8.0 Hz, 2H, Me₂NCH₂), 2.36 (s, 6H, N(CH₃)₂), 2.0-1.6(b, 2H, backbone CH₂), 1.82 (m, 2H, CH₂CH₂CH₂), 1.5-0.8 (b, 3H, CH₃).

23.3.2 3-(Dimethylamino)-1-Propylamine Functionalized PMMA (MW=120,000):

Polymethyl methacrylate (1.706 g, 17.0 mmol) was weighed into a 100 mLtwo-neck round bottom flask with a stir bar and evacuated on vacuumline/refilled with nitrogen three times. A reflux condenser was also putunder inert atmosphere using same procedure.3-(dimethylamino)-1-propylamine (10 mL) was added via syringe to thepolymer and a reflux condenser was placed onto flask. The mixture washeated to 150° C. for 16 hours under nitrogen. After this time, thereaction mixture was a light yellow liquid with yellow precipitate. Theliquid was decanted and the remaining light yellow solid was dried at80° C. under high vacuum for 2 hours. The solid was then broken up witha spatula until more of a powder formed and then re-dried using the sameconditions for another 2 hours. This step was repeated once more afterbreaking up brittle chunks of polymer using a mortar and pestle to givea fine powder (in order to facilitate drying). 2.065 g of yellow powderwas obtained and approximately 50% of the methacrylate sites werefunctionalized, as determined by integration of the appropriateresonances in the ¹H NMR spectrum.

¹H NMR (400 MHz, D₂O) δ 3.65 (bs, 3H, OCH₃), 2.81 (b, 2H, NHCH₂), 2.52(m, 2H, Me₂NCH₂), 2.31 (s, 6H, N(CH₃)₂), 2.0-1.6 (b, 2H, backbone CH₂),1.75 (m, 2H, CH₂CH₂CH₂), 1.3-0.7 (b, 3H, CH₃).

Large Scale Synthesis of 3-(Dimethylamino)-1-Propylamine FunctionalizedPMMA (MW=120,000):

Polymethyl methacrylate (47.14 g, 470.8 mmol) was weighed into a 1 L 2neck round bottom flask with a stir bar and fitted with a condenser andgas inlet. The apparatus was evacuated on vacuum line/refilled withnitrogen three times. 3-(dimethylamino)-1-propylamine (350 mL) waspoured into the flask under a flow of nitrogen. The mixture was heatedto 150° C. for 3.5 days under nitrogen. After stirring overnight thereaction mixture was observed to remain clear and colourless with awhite opaque gel precipitate. After full reaction time, the precipitatewas a more compact, clear solid. It was allowed to cool to roomtemperature and the liquid decanted. The solid was then dried at 90° C.under high vacuum for 2 hours causing it to swell. The swollen solid wasthen broken up with a spatula and drying continued for 3 hours beforebeing further broken up. Drying continued overnight. Very little of thehard crystalline mass was removed because it was difficult to do so. Inorder to soften solid it was heated to 170° C. under nitrogen beforebeing put under vacuum causing the solid to inflate. It was then driedovernight at 100° C. under full vacuum. Flask cooled, solid removed andground yielding 48.9 grams of white powder and approximately 80% of themethacrylate sites were functionalized, as determined by integration ofthe appropriate resonances in the ¹H NMR spectrum.

¹H NMR (400 MHz, D₂O) δ 3.64 (bs, 3H, OCH₃), 2.85 (t, J=8.0 Hz, 2H,NHCH₂), 2.56 (t, J=8.0 Hz, 2H, Me₂NCH₂), 2.34 (s, 6H, N(CH₃)₂),1.95-1.55 (b, 2H, backbone CH₂), 1.82 (m, 2H, CH₂CH₂CH₂), 1.5-0.7 (b,3H, CH₃).

3-(Dimethylamino)-1-Propylamine Functionalized PMMA (MW=350,000):

Polymethyl methacrylate (1.47 g, 14.7 mmol) was weighed into a 100 mLtwo-neck round bottom flask with a stir bar and evacuated on vacuumline/refilled with nitrogen three times. A reflux condenser was also putunder inert atmosphere using same procedure.3-(dimethylamino)-1-propylamine (15 mL) was added via syringe to thepolymer and a reflux condenser was placed onto flask. The mixture washeated to 150° C. for 5.5 days under nitrogen. After stirring overnight,the reaction mixture was a clear, colourless liquid with clear,colourless precipitate. The liquid was decanted and the remaining whitesolid was washed with 2-25 mL portions of isopropanol before being driedat 100° C. under high vacuum for 2 hours. The solid was then broken upwith a spatula until more of a powder formed and then re-dried using thesame conditions for another 2 hours. The solid was then ground into moreof a powder and dried for 2 hours, before being further ground and driedfor 16 hours. 0.888 g of white powder was obtained and approximately 80%of the methacrylate sites were functionalized, as determined byintegration of the appropriate resonances in the ¹H NMR spectrum.

¹H NMR (400 MHz, D₂O) δ 3.65 (bs, 3H, OCH₃), 2.84 (b, 2H, NHCH₂), 2.57(b, 2H, Me₂NCH₂), 2.35 (bs, 6H, N(CH₃)₂), 1.95-1.55 (b, 2H, backboneCH₂), 1.79 (b, 2H, CH₂CH₂CH₂), 1.5-0.7 (b, 3H, CH₃).

Neutral Polyacrylic Acid (PAA) Based Materials

All reactions were conducted in air unless stated otherwise. NMR spectrawere recorded on a Varian 400-MR NMR spectrometer (Agilent, Mississauga,Ontario, Canada). All NMR spectra are referenced against residualprotonated solvent.

Polyacrylic acid samples (MW=1,800 and 450,000) were purchased fromSigma Aldrich Inc. (Oakville, Ontario, Canada). Polyacrylic acid(MW=50,000) was purchased from Polysciences Inc. (Warrington, Pa., USA)as a 25% solution in water. This was dried under vacuum on a rotaryevaporator, washed with hexanes and dried further under vacuum givingthe polymer as a white solid. 3-dimethylam ino-1-propylamine waspurchased from Alfa Aesar (VWR, Mississauga, Ontario, Canada).

23.4.1 3-(Dimethylamino)-1-Propylamine Functionalized PAA (MW=1,800):

Polyacrylic acid (1.00 g, 13.88 mmol) was weighed into a 25 mL 2 neckround bottom flask with a stir bar and fitted with a gas inlet andrubber septum. The apparatus was evacuated on vacuum line/refilled withnitrogen three times. A reflux condenser was also put under inertatmosphere using same procedure. 3-(dimethylamino)-1-propylamine (1.57mL, 12.48 mmol) was added via syringe to the polymer and the refluxcondenser was placed onto the flask. The mixture was heated to 160° C.for 2.5 days under nitrogen. After that time, the reaction mixture was aslightly cloudy colourless solution and was allowed to cool to 100° C.causing it to become more cloudy and stirring difficult. The mixture wasdried at 100° C. for 6 hours under full vacuum followed by removal ofthe solid which was ground with a mortar and pestle giving a stickywhite solid. The solid was further dried at 80° C. under full vacuum for16 hours. The flask was cooled and 1.04 grams of white powder obtained.

¹H NMR (400 MHz, D₂O) δ 3.18 (m, 2H, NHCH₂), 2.41 (m, 2H, Me₂NCH₂), 2.24(s, 6H, N(CH₃)₂), 2.20-1.95 (b, 1H, backbone CH), 1.71 (m, 2H,CH₂CH₂CH₂), 1.70-1.20 (b, 2H, backbone CH₂).

23.4.2 3-(Dimethylamino)-1-Propylamine Functionalized PAA (MW=50,000):

Polyacrylic acid (1.00 g, 13.88 mmol) was weighed into a 50 mL 2 neckround bottom flask with a stir bar and fitted with a gas inlet andrubber septum. The apparatus was evacuated on vacuum line/refilled withnitrogen three times. A reflux condenser was also put under inertatmosphere using same procedure. 3-(dimethylamino)-1-propylamine (1.57mL, 12.48 mmol) was added via syringe to the polymer and the refluxcondenser was placed onto the flask. The mixture was heated to 160° C.for 24 hours under nitrogen. After that time, the reaction mixture was aclear yellow solution with stirring stopped. The mixture was dried at100° C. under full vacuum for 3 hours causing the solid to swell. Thissolid was broken up with a spatula and re-dried using the sameconditions for another 2 hours. The solid chunks were broken up in amortar and pestle giving a powder which was further dried for 24 hours.The flask was cooled and 1.42 grams of light yellow powder obtained.

¹H NMR (400 MHz, D₂O) δ 3.18 (m, 2H, NHCH₂), 2.42 (m, 2H, Me₂NCH₂), 2.29(s, 6H, N(CH₃)₂), 2.20-1.95 (b, 1H, backbone CH), 1.73 (m, 2H,CH₂CH₂CH₂), 1.80-1.25 (b, 2H, backbone CH₂).

23.4.3 3-(Dimethylamino)-1-Propylamine Functionalized PAA (MW=450,000):

Polyacrylic acid (1.00 g, 13.88 mmol) was weighed into a 50 mL 2 neckround bottom flask with a stir bar and fitted with a gas inlet andrubber septum. The apparatus was evacuated on vacuum line/refilled withnitrogen three times. A reflux condenser was also put under inertatmosphere using same procedure. 3-(dimethylamino)-1-propylamine (1.57mL, 12.48 mmol) was added via syringe to the polymer and the refluxcondenser was placed onto the flask. The mixture was heated to 160° C.for 2.5 days under nitrogen. After that time, stirring had stopped andthe reaction mixture remained a wet light yellow solid. The mixture wasdried at 100° C. under full vacuum for 4 hours giving a very hard solid.Parts of this solid were broken up with a spatula and re-dried using thesame conditions for another 16 hours. The solid chunks were ground upand further dried for 24 hours. The flask was cooled and 0.363 grams oflight yellow powder obtained.

¹H NMR (400 MHz, D₂O) δ 3.18 (m, 2H, NHCH₂), 2.41 (m, 2H, Me₂NCH₂), 2.27(s, 6H, N(CH₃)₂), 2.20-1.90 (b, 1H, backbone CH), 1.72 (m, 2H,CH₂CH₂CH₂), 1.85-1.25 (b, 2H, backbone CH₂).

Ionic Polyacrylic Acid (PAA) Based Materials

All reactions were conducted in air unless stated otherwise. NMR spectrawere recorded on a Varian 400-MR NMR spectrometer (Agilent, Mississauga,Ontario, Canada). All NMR spectra are referenced against residualprotonated solvent. Centrifugation was conducted with a Sorvall LegendXT laboratory centrifuge (Thermo Fisher Scientific, Ottawa, Ontario,Canada).

Polyacrylic acid samples (MW=1,800 and 450,000) were purchased fromSigma Aldrich Inc. (Oakville, Ontario, Canada). Polyacrylic acid(MW=50,000) was purchased from Polysciences Inc. (Warrington, Pa., USA)as a 25% solution in water. This was dried under vacuum on a rotaryevaporator, washed with hexanes and dried further under vacuum givingthe polymer as a white solid. 3-dimethylamino-1-propylamine waspurchased from Alfa Aesar (VWR, Mississauga, Ontario, Canada).(2-iodo-5-methoxyphenyl)boronic acid was prepared according to theliterature reference: Al-Zoubi, R. M.; Marion, O.; Hall, D. G. Angew.Chem. Int. Ed. 2008, 47, 2876.

All solvents were used as received. Methanol was purchased from ACPChemicals (Montreal, Quebec, Canada). Isopropanol was purchased fromCalcdon Laboratories (Georgetown, Ontario, Canada). Tetrahydrofuran waspurchased from EMD Chemicals (Gibbstown, N.J., US).

Ionic polymers were synthesized through a simple acid-base reactionbetween the acidic polymer and the basic amine yielding a salt of thepolycarboxylate with an ammonium counterion.

(Polyacrylic Acid), 3-(Dimethylamino)-1-Propylammonium Salt (MW=1,800)

Polyacrylic acid (1.00 g, 13.88 mmol) was added to a 100 mLround-bottomed flask. Methanol (20 mL) was added and stirred giving aclear, colourless solution. 3-(dimethylamino)-1-propylamine (1.75 mL,13.91 mmol) was added dropwise via syringe causing the immediateprecipitation of a thick white solid which then disappeared after a fewminutes. The solution was stirred overnight at 20° C. under air. Thesolvent was removed using a rotary evaporator giving a clear, colourlessoil which was re-dissolved in 3 mL methanol. This concentrated solutionwas added dropwise to 500 mL of rapidly stirred tetrahydrofuran giving awhite suspension which was stirred for 30 minutes before being allowedto settle. Most of the supernatant was decanted with the remaining 50 mLbeing transferred to a Nalgene bottle and centrifuged at 2000 rpm for 60minutes. Remainder of supernatant decanted and solid dried under fullvacuum at 20° C. for 4 hours. 1.05 grams of fine white powder isolated.

¹H NMR (400 MHz, D₂O) δ 3.08 (m, 4H, NHCH₂ and Me₂NCH₂), 2.77 (s, 6H,N(CH₃)₂), 2.30-1.95 (b, 1H, backbone CH), 2.08 (m, 2H, CH₂CH₂CH₂),1.90-1.20 (b, 2H, backbone CH₂).

(Polyacrylic Acid), 3-(Dimethylamino)-1-Propylammonium Salt (MW=1,800):

Polyacrylic acid (1.51 g, 20.95 mmol) and(2-iodo-5-methoxyphenyl)boronic acid (0.291 g, 1.05 mmol) were added toa 500 mL Schlenk round-bottomed flask under nitrogen flush.Tetrahydrofuran (125 mL) was added and stirred for 30 minutes graduallygiving a colorless, clear solution. 3-(dimethylamino)-1-propylamine(5.27 mL, 41.88 mmol) was then added via syringe resulting in theimmediate formation of a thick white slurry. The resultant suspensionwas stirred for 2.5 days at 20° C. under nitrogen. The cloudy, whitemixture was filtered through a Büchner funnel and the collected whitesolid was washed with 2-50 mL portions of tetrahydrofuran. The filterpaper and solid were placed in a dessicator and dried under full vacuumat 20° C. for 6 hours. 2.20 grams of white solid were removed from thefilter paper and crushed in a mortar and pestle giving a fine whitepowder which was judged to be suitably dry.

¹H NMR (400 MHz, D₂O) δ 3.01 (t, J=8.0 Hz, 2H, NHCH₂), 2.91 (t, J=8.0Hz, 2H, Me₂NCH₂), 2.62 (s, 6H, N(CH₃)₂), 2.20-1.95 (b, 1H, backbone CH),1.99 (m, 2H, CH₂CH₂CH₂), 1.80-1.20 (b, 2H, backbone CH₂).

(Polyacrylic Acid), 3-(Dimethylamino)-1-Propylammonium Salt (MW=50,000):

Polyacrylic acid (1.51 g, 20.95 mmol) and(2-iodo-5-methoxyphenyl)boronic acid (0.291 g, 1.05 mmol) were added toa 500 mL Schlenk round-bottomed flask under nitrogen flush. Methanol(200 mL) was added and stirred for 30 minutes gradually giving acolorless, clear solution. 3-(dimethylamino)-1-propylamine (5.27 mL,41.88 mmol) was then added via syringe resulting in the immediateformation of a white suspension. The white solid redissolved overseveral minutes giving a clear and colorless solution. The reactionmixture was stirred overnight at 20° C. under nitrogen. The solution wasdecanted to a 500 mL round-bottomed flask and concentrated under vacuumgiving a clear, semi-viscous liquid. The liquid was added dropwise to900 mL of rapidly stirred isopropanol immediately giving a fine whitesolid. The stirring was stopped after 30 minutes but little solidsettled so supernatant was transferred to Nalgene bottles andcentrifuged at 2000 rpm for 1 hour causing complete separation ofsupernatant and white gel. The supernatant was decanted, the fourNalgene bottles placed inside a desiccator and dried overnight at 20° C.under high vacuum. The solid was then broken up using a mortar andpestle and dried at 80° C. for several hours giving 1.62 g of whitepowder.

¹H NMR (400 MHz, D₂O) δ 3.19 (t, J=8.0 Hz, 2H, NHCH₂), 3.07 (t, J=8.0Hz, 2H, Me₂NCH₂), 2.85 (s, 6H, N(CH₃)₂), 2.2-1.9 (b, 1H, backbone CH),2.12 (m, 2H, CH₂CH₂CH₂), 1.75-1.25 (b, 2H, backbone CH₂).

(Polyacrylic Acid), 3-(Dimethylamino)-1-Propylammonium Salt(MW=450,000):

Polyacrylic acid (1.51 g, 20.95 mmol) and(2-iodo-5-methoxyphenyl)boronic acid (0.291 g, 1.05 mmol) were added toa 500 mL Schlenk round-bottomed flask under nitrogen flush. Methanol(200 mL) was added and stirred for 30 minutes gradually giving acolorless, clear solution. 3-(dimethylamino)-1-propylamine (5.27 mL,41.88 mmol) was then added via syringe resulting in the immediateformation of a white suspension. The white solid started to amalgamateafter 1 minute into a lump which then proceeded to decrease in size overseveral minutes giving a clear and colorless solution. The reactionmixture was stirred overnight at 20° C. under nitrogen. The slightlycloudy solution was decanted to a 500 mL round-bottomed flask andconcentrated under vacuum giving a clear, semi-viscous liquid. Theliquid was added dropwise to 900 mL of rapidly stirred isopropanolimmediately giving a white gel-like solid. Most of the supernatant wasdecanted while remaining suspension was transferred to Nalgene bottlesand centrifuged at 2000 rpm for 1 hour causing complete separation ofsupernatant and white gel. The supernatant was decanted, the two Nalgenebottles placed inside a desiccator and dried overnight at 20° C. underhigh vacuum. The solid was then broken up using a mortar and pestle anddried at 80° C. for several hours giving 1.61 g of white powder.

¹H NMR (400 MHz, D₂O) δ 3.20 (m, 2H, NHCH₂), 3.09 (m, 2H, Me₂NCH₂), 2.87(s, 6H, N(CH₃)₂), 2.2-1.95 (b, 1H, backbone CH), 2.13 (m, 2H,CH₂CH₂CH₂), 1.75-1.25 (b, 2H, backbone CH₂).

23.5 Polymethyl Methacrylate-Co-Styrene (PMMA/PS) Based Materials

All reactions were conducted in air unless stated otherwise. NMR spectrawere recorded on a Varian 400-MR NMR spectrometer (Agilent, Mississauga,Ontario, Canada). All NMR spectra are referenced against residualprotonated solvent.

Polystyrene-co-polymethyl methacrylate (1.4, 10, 20, and 31 mol %styrene) were purchased from Polymer Source (Montreal, Quebec, Canada).Polystyrene-co-polymethyl methacrylate (40 mol % styrene) was purchasedfrom Sigma Aldrich Inc. (Oakville, Ontario, Canada).3-dimethylamino-1-propylamine was purchased from Alfa Aesar (VWR,Mississauga, Ontario, Canada).

All solvents were used as received. Isopropanol was purchased fromCalcdon Laboratories (Georgetown, Ontario, Canada).

23.5.1 3-(Dimethylamino)-1-Propylamine Functionalized PMMA/PS (40 mol %Styrene, MW=100,000-150,000):

Polystyrene-co-methyl methacrylate (2.938 g) was added to a 100 mL 2neck round bottom flask and evacuated on vacuum line/refilled withnitrogen three times. Separately a reflux condenser was also put underan inert atmosphere using the same procedure.3-(dimethylamino)-1-propylamine (20 mL) was added via syringe and thereflux condenser was placed onto the flask. The mixture was heated to150° C. overnight under nitrogen. The resulting yellow solution wascooled to only 80° C. so that its viscosity didn't increasesignificantly; the solution was decanted slowly into 900 mL of rapidlystirred isopropanol giving a white-yellow precipitate that was filteredthrough a Buchner funnel. The polymer was dried at 80° C. under highvacuum for several hours giving a solid chunk, which was broken up witha mortar and pestle giving a light yellow solid. This was driedovernight at 80° C. under high vacuum. 2.85 grams of light yellow,water-insoluble powder was obtained.

¹H NMR (400 MHz, CDCl₃) δ 7.2-6.7 (b, 5H, aromatic CH), 3.52 (bs, 3H,OCH₃), 2.80 (b, 2H, NHCH₂), 2.39 (b, 2H, Me₂NCH₂), 2.23 (s, 6H,N(CH₃)₂), 2.1-1.4 (b, backbone CH₂ and CH), 1.68 (b, 2H, CH₂CH₂CH₂),1.0-0.3 (b, backbone CH and CH₃).

23.5.2 3-(Dimethylamino)-1-Propylamine Functionalized PMMA/PS (31 mol %Styrene, MW=117,000-192,000):

Polystyrene-co-methyl methacrylate (1.13 g) was added to a 100 mL 2 neckround bottom flask and evacuated on vacuum line/refilled with nitrogenthree times. Separately a reflux condenser was also put under an inertatmosphere using the same procedure. 3-(dimethylamino)-1-propylamine (15mL) added via syringe and the reflux condenser was placed onto theflask. The mixture was heated to 150° C. overnight under nitrogen. Theresulting clear, colorless solution was cooled to 20° C. causing a whitegel to precipitate. The supernatant was decanted and the gel was washedwith two 50 mL portions of isopropanol before being dried at 80° C. for2 hours under high vacuum. The solid then broken up and drying wascontinued for another 2 hours under high vacuum. The solid was thenbroken up using a mortar and pestle and drying was continued overnightat 80° C. under high vacuum. 1.09 grams of white, water-insoluble powderwas obtained.

¹H NMR (400 MHz, CDCl₃) d 7.3-6.8 (b, 5H, aromatic CH), 3.55 (bs, 3H,OCH₃), 2.83 (b, 2H, NHCH₂), 2.42 (b, 2H, Me₂NCH₂), 2.26 (s, 6H,N(CH₃)₂), 2.0-1.5 (b, backbone CH₂ and CH), 1.71 (b, 2H, CH₂CH₂CH₂),1.2-0.4 (b, backbone CH and CH₃).

23.5.3 3-(Dimethylamino)-1-Propylamine Functionalized PMMA/PS (20 mol %Styrene, MW=146,000-230,000):

Polystyrene-co-methyl methacrylate (1.075 g) was added to a 100 mL 2neck round bottom flask and evacuated on vacuum line/refilled withnitrogen three times. Separately a reflux condenser was also put underan inert atmosphere using the same procedure.3-(dimethylamino)-1-propylamine (15 mL) added via syringe and the refluxcondenser was placed onto the flask. The mixture was heated to 150° C.overnight under nitrogen. The yellow solution was cooled to 80° C.causing a yellow gel to precipitate. The supernatant was decanted andthe yellow thick gel was washed with two 50 mL portions of isopropanolbefore being dried at 80° C. for 2 hours under high vacuum. The solidwas then broken up and drying continued for another 2 hours under highvacuum. The solid was then broken up using a mortar and pestle anddrying was continued overnight at 80° C. under high vacuum. 1.15 gramsof light yellow, water-soluble powder was obtained.

¹H NMR (400 MHz, D₂O) δ 7.5-6.8 (b, 5H, aromatic CH), 3.64 (bs, 3H,OCH₃), 2.76 (b, 2H, NHCH₂), 2.48 (b, 2H, Me₂NCH₂), 2.27 (s, 6H,N(CH₃)₂), 2.2-1.7 (b, backbone CH₂ and CH), 1.72 (b, 2H, CH₂CH₂CH₂),1.4-0.5 (b, backbone CH and CH₃).

23.5.4 PMMA/PS (10 mol % Styrene, MW=10,600-15,900):

Polystyrene-co-methyl methacrylate (1.15 g, MW=10,600-15,900) was addedto a 100 mL 2 neck round bottom flask and evacuated on vacuumline/refilled with nitrogen three times. Separately a reflux condenserwas also put under an inert atmosphere using the same procedure.3-(dimethylamino)-1-propylamine (15 mL) was added via syringe and thereflux condenser was placed onto the flask. The mixture was heated to150° C. overnight under nitrogen. The resulting yellow solution wascooled to 80° C. causing a yellow gel to precipitate. The supernatantwas decanted and the yellow thick gel was washed with two 50 mL portionsof isopropanol before being dried at 80° C. for 2 hours under highvacuum. The solid was then broken up and drying was continued foranother 2 hours under high vacuum. The solid was then broken up using amortar and pestle and drying was continued overnight at 80° C. underhigh vacuum. 1.07 grams of light yellow, water-soluble powder wasobtained.

¹H NMR (400 MHz, D₂O) δ 7.45-7.0 (b, 5H, aromatic CH), 3.65 (bs, 3H,OCH₃), 2.85 (t, J=8.0 Hz, 2H, NHCH₂), 2.56 (b, 2H, Me₂NCH₂), 2.34 (s,6H, N(CH₃)₂), 2.1-1.6 (b, backbone CH₂ and CH), 1.79 (m, 2H, CH₂CH₂CH₂),1.6-0.6 (b, backbone CH and CH₃).

23.5.5 PMMA/PS (1.4 mol % Styrene, MW=9,200-12,900):

Polystyrene-co-methyl methacrylate (1.09 g) was added to a 100 mL 2 neckround bottom flask and evacuated on vacuum line/refilled with nitrogenthree times. Separately a reflux condenser was also put under an inertatmosphere using the same procedure. 3-(dimethylamino)-1-propylamine (15mL) was added via syringe and the reflux condenser was placed onto theflask. The mixture heated to 150° C. overnight under nitrogen. Theresulting yellow solution was cooled to room temperature causing a whitegel to precipitate. The supernatant was decanted and the yellow thickgel was washed with three 50 mL portions of isopropanol before beingdried at 80° C. for 2 hours under high vacuum. The solid was then brokenup and drying was continued for another 2 hours under high vacuum. Thesolid was then broken up using a mortar and pestle and drying wascontinued overnight at 80° C. under high vacuum. 0.469 grams of white,water-soluble powder was obtained.

¹H NMR (400 MHz, D₂O) δ 7.4-7.0 (b, 5H, aromatic CH), 3.64 (bs, 3H,OCH₃), 2.86 (t, J=8.0 Hz, 2H, NHCH₂), 2.57 (b, 2H, Me₂NCH₂), 2.35 (s,6H, N(CH₃)₂), 2.2-1.5 (b, backbone CH₂ and CH), 1.79 (m, 2H, CH₂CH₂CH₂),1.5-0.5 (b, backbone CH and CH₃).

Polydiethylaminoethylmethacrylate (PDEAEMA) Based Materials

2-(diethylamino)ethyl methacrylate was purchased from Sigma-Aldrich,2,2′-azobis[2-(2-imidazolin-2-yl)propane] was purchased from Wako PureChemical Industries, Ltd. THF was purchased from Fisher Scientific. Sizeexclusion chromatography (SEC) was conducted using a Waters 2960separation module with Styragel packed columns HR 0.5, HR 1, HR 3, HR 4,and HR 5E (Waters Division Millipore) coupled with a refractive indexdetector operating at 40° C.

Polydiethylaminoethylmethacrylate (PDEAEMA) MW=55,000

5.42 mL (5.0 g, 27.0 mmol) 2-(Diethylamino)ethyl methacrylate was placedin a 100 mL 2-neck round-bottom flask equipped with a 1 cm stir bar, aseptum and condenser. 30 mL of THF and 0.050 g of2,2′-azobis[2-(2-imidazolin-2-yl)propane] were added. The reactionmixture was degassed at room temperature by bubbling argon through thesolution using a single gauge needle under stirring with 600 rpm. After1 h the needle was removed and the reaction mixture was heated to 65° C.for 5 h. After cooling to room temperature the solution was poured intoa beaker equipped with a stir bar and 100 mL of cold water. The polymerprecipitated over the 16 h under stirring to form a sticky gum-likesolid that was collected with a spatula and dried in a dessicator for 24h. The product was obtained as a sticky gum (2.7 g 54%)

¹H NMR (400 MHz, CDCl₃): δ=4.12-3.91 (m, 2H, OCH₂), 2.74-2.66 (m, 2H,CH₂CH₂N), 2.62-2.48 (m, 4H, CH₃CH₂N), 2.00-1.74 (m, 2H, CH₂ backbone),1.14-0.96 (m, 6H, CH₃CH₂N), 0.95-0.82 (CCH₃);

¹³C NMR (100.7 MHz, CDCl₃): δ=177.4, 63.1 (OCH₂), 50.4 (CH₂CH₂N), 47.6(CH₃CH₂N), 18.5 (CH₂ backbone), 16.6 (CCH₃), 12.0 (CH₃CH₂N);

GPC: (THF): M_(n): 31000, M_(w): 55,000, PDI: 1.78.

23.6.2 Polydiethylaminoethylmethacrylate (PDEAEMA) MW=69,000

5.42 mL (5.0 g, 27.0 mmol) 2-(diethylamino)ethyl methacrylate was placedin a 100 mL 2-neck round-bottom flask equipped with a 1 cm stir bar, aseptum and condenser. 15 mL of THF and 0.050 g of2,2′-azobis[2-(2-innidazolin-2-yl)propane] were added. The reactionmixture was degassed at room temperature by bubbling argon through thesolution using a single gauge needle under stirring with 600 rpm. After1 h the needle was removed and the reaction mixture was heated to 65° C.for 5 h. After cooling to room temperature the solution was poured intoa beaker equipped with a stir bar and 100 mL of cold water. The polymerprecipitated over the 16 h under stirring to form a sticky gum-likesolid that was collected with a spatula and dried in a dessicator for 24h. The product was obtained as a sticky gum (2.0 g, 40%)

¹H NMR (400 MHz, CDCl₃): δ=4.12-3.91 (m, 2H, OCH₂), 2.74-2.66 (m, 2H,CH₂CH₂N), 2.62-2.48 (m, 4H, CH₃CH₂N), 2.00-1.74 (m, 2H, CH₂ backbone),1.14-0.96 (m, 6H, CH₃CH₂N), 0.95-0.82 (CCH₃);

¹H NMR (100.7 MHz, CDCl₃): δ=177.4, 63.1 (OCH₂), 50.4 (CH₂CH₂N), 47.6(CH₃CH₂N), 18.5 (CH₂ backbone), 16.6 (CCH₃), 12.0 (CH₃CH₂N);

GPC: (THF): M_(n): 39000, M_(w): 69,000, PDI: 1.76.

Switchable Solubility of Polydiethylaminoethylmethacrylate (PDEAEMA)MW=69,000

800 mg of polydiethylaminoethylmethacrylate (PDEAEMA) MW=69000 wasplaced in a 100 mL round bottom flask equipped with a 1 cm stir bar. 60mL of deionized water was added, CO₂ was introduced by means of a glassdispersion tube at 1 atm and the mixture was stirred at 900 rpm for 5 hat 50° C. Then the dispersion tube was removed, the flask closed with aglass stopper and the mixture was stirred for another 16 h at 50° C. Thesolution was then filtered off and the undissolved polymer weighed. 200mg of the polymer did not dissolve. Therefore, the polymer has asolubility of 600 mg in 60 mL of carbonated water.

The solution was then bubbled with argon under heating at 60° C. After10 min the solution turned turbid, and after 30 min, precipitate wasvisible. Bubbling with argon under heat was continued for another 30min. Then the polymer was collected by filtration and the waterevaporated. This left behind 5 mg of a solid that was analyzed by NMR.The NMR only showed traces of the polymer. The solubility of the polymerin water is therefore <1%.

Example 24 Viscosity Control with Switchable Water Additives

In order to study the use of switchable water additives in a method andsystem for viscosity control, a switchable additive or other molecule ofinterest was placed in a 50 mL round-bottom flask equipped with a 1 cmmagnetic stir-bar and placed on a stir-plate. Water was added and themixture was agitated at 600 rpm until the polymer was completelydissolved (1-24 h). The solution was then transferred in to a TechnicalGlass Products, Inc. C. F. Opage viscometer with either a 100 or 200capillary tube. The measurements were taken at room temperature (i.e.,from about 15-30° C.) and repeated twice. The solution was transferredback into the round bottom flask and CO₂ was introduced to the mixtureby bubbling for 30 minutes at a flow rate of 80 ml/min. The carbonatedsolution was then put into the viscometer and the viscosity was measuredthree times. The viscosity in centistokes (cS) was calculated from thetimes the solution took to run through the viscometer.

24.1 Switchable Viscosity Using 3-(Dimethylamino)-1-PropylamineFunctionalized Polymethylmethacrylate (MW=120,000)

Using the general method described above, 207.3 mg of PMMA (120,000) wasdissolved in 20 mL H₂O and stirred for 1 h. Measurements were taken onthe 200 viscometer. The viscosity change was reversed by removing theCO₂ through bubbling of Ar at 40° C. for 30 min. Measurements were takenagain, leading to similar results obtained for the first run with no CO₂present.

without CO₂ with CO₂ viscosity 8.3 cS 1.4 cS

24.2 Switchable Viscosity Using 3-(Dimethylamino)-1-PropylamineFunctionalized Polymethylmethacrylate (MW=35,000)

Using the general method described above, 100.6 mg of PMMA (35,000) wasdissolved in 10 mL H₂O and stirred for 1 h. Measurements were taken onthe 200 viscometer.

without CO₂ with CO₂ viscosity 1.7 cS 1.2 cS

24.3 Switchable Viscosity Using Ionic Polyacrylic Acid (MW=450,000)

Using the general method described above, 54.9 mg of the ionic PAA(450,000) was dissolved in 10 mL H₂O and stirred for 1 h. Measurementswere taken on the 200 viscometer.

without CO₂ with CO₂ viscosity 10.5 cS 4.0 cS

24.4 Switchable Viscosity Control Experiment Using Polyacrylamide (MW:6,000,000)

Using the general method described above, 33.3 mg of polyacrylamide (MW:6,000,000) was dissolved in 10 mL H₂O and stirred for 1 h. Measurementswere taken on the 200 viscometer.

without CO₂ with CO₂ viscosity 6.9 cS 6.7 cS

These results demonstrate that the introduction of CO₂ did not changethe viscosity of a solution of a non-switchable water polymer, even whenthe polymer was a very high molecular weight polymer.

24.5 Switchable Viscosity Control Experiment UsingN,N-Dimethylcyclohexylamine

Using the general method described above, 104.6 mg ofN,N-dimethylcyclohexylamine was dissolved in 10 mL H₂O and stirred for 1h. Measurements were taken on the 100 viscometer.

without CO₂ with CO₂ viscosity 1.0 cS 1.0 cS

These results demonstrate that the introduction of CO₂ does not changethe viscosity of a solution comprising a switchable water additivehaving a molecular weight that is too low to generate a substantialviscosity increase over water alone (which has a viscosity of about 1.0cS at 20° C.), when the switchable water additive is in the non-ionizedform.

24.6 Switchable Viscosity Using 3-(Dimethylamino)-1-PropylamineFunctionalized PMMA/PS (PS 10 mol %, MW=10,600-15,900)

Using the general method described above, 150 mg of3-(dimethylamino)-1-propylamine functionalized PMMA/PS (PS 10 mol %) wasdissolved in 7.5 mL H₂O and stirred for 1 h. Measurements were taken onthe 100 viscometer.

without CO₂ with CO₂ viscosity 1.4 cS 1.1 cS

In this study, the switchable additive 3-(dimethylamino)-1-propylaminefunctionalized PMMA/PS (PS 10 mol %) has a lower molecular weight thanthe additives tested above. As a result, the difference in viscositybetween water alone and water plus the switchable additive3-(dimethylamino)-1-propylamine functionalized PMMA/PS (PS 10 mol %) isnot as large as the difference observed using the polyamine switchableadditives tested above. This study demonstrates a decrease in viscosityfollowing the addition of CO₂, despite the fact that the presence of thenon-ionic form of the switchable additive causes only a modest increasein viscosity over water alone. However, even with low molecular weightpolymers, increasing the concentration of the polymer in a sample canalso have a large effect on viscosity and, therefore, the relativechange in viscosity when the additive is switched.

As demonstrated in this example, switchable water can be usedeffectively in a system having switchable viscosity. Selection of theappropriate switchable additive will, in part, depend on the degree ofviscosity change required. If a large viscosity change is required, theswitchable additive should have a relatively large molecular weightwhile remaining sufficiently soluble in water when in its non-ionic formto generate a substantial increase in viscosity in comparison to theviscosity of water alone. In systems where only a small viscosity changeis desired, then the switchable water additive should be selected tohave a relatively low molecular weight and be sufficiently soluble inwater when in its non-ionic form to generate an increase in viscosity incomparison to the viscosity of water alone.

Example 25 Reversible Solvent Miscibility with Switchable WaterAdditives

25.1 Ceiling Salting Out Limits

NaCl, (NH₄)₂SO₄, d3-MeCN, MeOD were all purchased from Sigma Aldrich,Oakville. THF, ethyl acetate and acetonitrile were purchased from FisherScientific, Ottawa. Aliquots were taken using a Mettler-Toledo pipetor,all ¹H NMR acquired on a 400 MHz Bruker instrument.

Approximately 2 g of an organic solvent and approximately 2 g of waterwere mixed in a graduated cylinder. Small amounts of either NaCl or(NH₄)₂SO₄ were added to the solution to induce a salting out of theorganic. Salt was continually added until the salted out organicmaintained a constant volume above the aqueous layer. The volumes ofeach phase were recorded. Additional salt was often added past theobservation of a consistent volume and no additional volume changeoccurred.

A 50 μL aliquot of the aqueous phase was extracted and placed in an NMRtube. The sample was diluted with a deuterated solvent. Approximately 20mg of ethyl acetate was added to the NMR tube to act as an internalstandard. A ¹H NMR spectrum was acquired and the peaks integrated.Knowing the amount of ethyl acetate and its corresponding integrations,the amount of organic solvent in the aqueous aliquot was calculated andmultiplied to reflect the total amount of organic solvent still in theaqueous layer. Subtracting this value from the total mass of the organicsolvent used in the experiment provided a ceiling percentage of organicsolvent that could be salted out with inorganic salts. This experimentwas carried out in triplicate using both salts for THF and acetonitrile.The results are presented in the table below.

Solvent Salt % Organic Salted Out THF NaCl 98 ± 0.5% THF (NH₄)₂SO₄ 99 ±0.6% MeCN NaCl 93 ± 1.0% MeCN (NH₄)₂SO₄ 99 ± 0.1%

25.2 Acetonitrile-Water Forcing Out

Polyamines were investigated as additives for switchable ionic strengthsolutions useful in forcing out acetonitrile from an aqueous phase. Tomeasure the extent of acetonitrile being forced out of an aqueous phaseby an increase in ionic strength, and the amounts of polyamine thatremained in the aqueous phase, 1:1 w/w solutions of acetonitrile andwater were prepared in graduated cylinders. Three hundred milligrams ofthe additive were added and the cylinders were capped with rubber septa.After 30 minutes of bubbling carbon dioxide through the liquid phasefrom a single narrow gauge steel needle, a visible phase separation wasobserved. The volumes of each phase were recorded. Aliquots of thenon-aqueous and aqueous layers were taken and dissolved in D₂O in NMRtubes. A known amount of dimethylformamide (DMF) was added to each NMRtube as an internal standard. ¹H NMR spectra were acquired and throughintegration of the DMF standard, a concentration of acetonitrile oradditive was calculated and scaled up to reflect the total volume of theaqueous or non-aqueous phase, giving a percentage of the compound beingforced out or retained.

Acetonitrile Polymer retained Polymer forced out in aqueous phase EPEI(MW = 600) 60% 87% EPEI (MW = 1,800) 56% 71% EPEI (MW = 10,000) 55% 73%3-(dimethylamino)-1-propylamine 66% 99% functionalized PMMA (MW =35,000) 3-(dimethylamino)-1-propylamine 65-75%    99% functionalizedPMMA (MW = 120,000) Polydiallylmethylamine 72% 99% Ionic PAA (MW =1,800) 76% 99%

Following phase separation and collection of samples from each phase,argon was bubbled through the mixture while heating to 50° C. until thetwo phases recombined (typically from 15 to 60 min). The switchingprocess (i.e., 30 min of CO₂ bubbling, sample collection, then 30 min ofAr bubbling) was successfully repeated, demonstrating that thereversible process can be cycled.

25.3 THF-Water Forcing Out

Polyamines were investigated as additives for switchable ionic strengthsolutions useful in forcing out THF from an aqueous phase. To measurethe extent of THF being forced out of an aqueous phase by an increase inionic strength, and the amounts of polyamine that remained in theaqueous phase, 1:1 w/w solutions of THF and water were prepared ingraduated cylinders. Three hundred milligrams of the additive were addedand the cylinders were capped with rubber septa. After 30 minutes ofbubbling carbon dioxide through the liquid phase from a single narrowgauge steel needle, a visible phase separation was observed. The volumesof each phase were recorded. Aliquots of the non-aqueous and aqueouslayers were taken and dissolved in acetonitrile-d₃ in NMR tubes. A knownamount of ethylacetate (EtOAc) was added to each NMR tube as an internalstandard. ¹H NMR spectra were acquired and through integration of theEtOAc standard, a concentration of THF or additive was calculated andscaled up to reflect the total volume of the aqueous or non-aqueousphase, giving a percentage of the compound being forced out or retained.

Polymer retained Polymer THF forced out in aqueous phase EPEI (MW = 600)76% 99% Functionalized PMMA 79% 99% (MW = 35,000)

Then argon was bubbled through the solution while heating to 50° C.until the two phases recombined (15 to 60 min). The switching process(i.e., 30 min of CO₂ bubbling, sample collection, then 30 min of Arbubbling) was successfully repeated, demonstrating that the reversibleprocess can be cycled.

25.4 Solvent Bridging with Switchable Water Additive

25.4.1 Ethyl Acetate & Water: CO₂-Induced Phase Separation:

0.531 g H₂O was mixed with 0.517 g ethyl acetate, generating a biphasicsolution. The addition of 0.319 g N,N,A/W-tetramethyl-1,4-diaminobutane(TMDAB) bridged the two solvents into a single phase, clear, colourlesssolution (5:3:5 w/w/w H₂O:amine:organic). A stream of CO₂ was run overtop of the solution for 5 minutes where an organic liquid phase began tocream out of the original monophasic solution.

25.4.2 n-Octanol & Water:

0.515 g H₂O was mixed with 0.315 g n-octanol, generating a biphasicsolution. The addition of 0.498 gN,N,N′,N′-tetramethyl-1,4-diaminobutane (TMDAB) bridged the two solventsinto a single phase, clear, colourless solution (5:5:3 w/w/wH₂O:amine:organic). A stream of CO₂ was run over top of the solution for5 minutes where an organic liquid phase began to cream out of theoriginal monophasic solution.

The above results demonstrate the successful use of switchable water ina system and method for reversing organic solvent miscibility. In such asystem and method the switchable additive is selected such that itremains soluble in water when in its ionized form, but it is notnecessary for the additive to be soluble in water when in thenon-ionized form. In fact, in certain embodiments it may be beneficialfor the additive to be insoluble or immiscible with water when it is inits non-ionized form. Additionally, in order to maximize the separationbetween the aqueous phase and the organic phase, the majority ofadditive should be retained in the aqueous layer when it is in itsionized form. That is, the ionized form of the additive should exhibitlittle or no solubility/miscibility with the organic solvent or littleor no tendency to partition into the organic solvent from water.

Example 26 Solvent Drying with Switchable Water Additives

THF was from Fisher Scientific, Ottawa. CO₂ from Praxair, Belleville.Water content was determined on a Mettler-Toledo C20 coulometricKarl-Fischer titrator using a Hydranal Coulomat AK solution from SigmaAldrich, Oakville. Samples were centrifuged on a Thermo Scientific IECMedilite Centrifuge.

26.1 Dehydration of THF Using a Polymer

In a glass vial containing a stirbar, 102.8 mg of3-(dimethylamino)-1-propylamine-functionalized poly(methylmethacrylate-co-styrene) (40 mol % styrene, MW=100,000-150,000) wasdissolved a solution of 3.598 g THF (Fisher Scientific) and 0.398 gwater (˜9:1 THF:H₂O w/w). The THF contained ˜1 wt % water as determinedby Karl-Fischer titration so the initial water content of the solutionwas approximately 109,000 ppm. The vial was capped with a rubber septumand a single narrow gauge steel needle was inserted through the septuminto the solution. A second needle was inserted into the septum, but notinto the solution, to act as a gas outlet. CO₂ was introduced into thesolution through the first needle at a flow rate of ˜10-20 mL min⁻¹ for60 minutes while stirring. Some small white precipitate immediatelyformed and more formed during the course of CO₂ treatment. After 60minutes, the needles were withdrawn and the vial was sealed and left tosit for several hours.

The solids did not settle out after a few hours so the mixture wascentrifuged at 3100 RPM for 5 minutes causing the precipitate to settle.The liquid was decanted off and the water content analyzed byKarl-Fischer titration. The solution was found to have a water contentof roughly 91,000 ppm, resulting in ˜17 of the water being removed viathe polymer precipitate from CO₂ treatment.

26.2 Dehydration of Isobutanol Using a Polymer at Various Loadings

Isobutanol was from Sigma Aldrich, Oakville. CO₂ from Praxair,Belleville. Water content was determined on a Mettler-Toledo C20coulometric Karl-Fischer titrator using a Hydranal Coulomat AK solutionfrom Sigma Aldrich, Oakville.

Solutions of 4.5 g isobutanol and 0.5 g H₂O were made up in fiveseparate glass vials containing stirbars. Varied amounts of3-(dimethylamino)-1-propylamine-functionalized polymethyl methacrylate(MW=35,000) were dissolved into each solution. Vial 4 and 5 were blanks,with vial 4 containing the above polymer (with no later CO₂ treatment)and vial 5 containing unfunctionalized polymethyl methacrylate. Themajority of the unfunctionalized polymethyl methacrylate did notdissolve in this solution. The initial water content of each vial wasroughly 100,000 ppm.

Vial Loading of Polymer 1  50.4 mg 2 102.5 mg 3 150.8 mg  4* 103.8 mg 5**  99.5 mg *Functionalized polymer with no CO₂ treatment,**Unfunctionalized polymer with no CO₂ treatment.

Vials 1-3 were capped with rubber septa and a single narrow gauge steelneedle was inserted through the septa into each solution. A secondneedle was inserted into the septa, but not into the solution, to act asa gas outlet. CO₂ was introduced into each solution through the firstneedle at a flow rate of ˜10-20 mL min⁻¹ for 30 minutes while stirring.Small white precipitate immediately formed and more formed during thecourse of CO₂ treatment. After 30 minutes, the needles were withdrawnand the vial was sealed and left to sit for 18 hours. Vials 4 and 5 werecapped under air and left to sit for 18 hours.

After 18 hours, the liquid was removed from each vial and analyzed byKarl-Fischer titration. The remaining polymer that precipitated or didnot dissolve initially was dried in a 120° C. oven overnight at 7 mm Hgpressure. The water content of the solutions after treatment and polymerrecovered after treatment are described below.

Final Water % Water % Polymer Vial Content Removed Recovered 1 94,000ppm 6% 56% 2 91,000 ppm 9% 44% 3 77,000 ppm 23%  45%  4* ~100,000 ppm 0% 0%  5** ~100,000 ppm 0% 65% *Functionalized polymer with no CO₂treatment, **Unfunctionalized polymer with no CO₂ treatment.

26.3 Dehydration of a Mixed Organic Solvent with Polymers

Toluene and xylenes were purchased from Fisher Scientific, Ottawa.Silica and methyl ethyl ketone were from Sigma Aldrich, Oakville.Ethanol was from Commerical Alcohols, Brampton and CO₂ was from Praxair,Belleville. Water content was determined on a Mettler-Toledo C20coulometric Karl-Fischer titrator using a Hydranal Coulomat AK solutionfrom Sigma Aldrich, Oakville.

In a glass vial containing a stirbar, 49.2 mg of3-(dimethylamino)-1-propylannine-functionalized poly (methylmethacrylate-co-styrene) (40 mol % styrene, MW=100,000-150,000) wasdissolved in 1.900 g 3:3:3:1 v/v methyl ethylketone:toluene:xylenes:ethanol. The addition of 0.102 g water (to give a−19:1 organic:H₂O w/w solution) caused some polymer to precipitate outof solution. The initial water content of the mixture was 51,000 ppm;however the actual amount of water dissolved into the organic solventresulted in organic solution with a water content of −17,000 ppm. Thevial was capped under air, stirred for 60 minutes and then left to sitfor 24 hours.

In a 2^(nd) glass vial container a stirbar, 50.1 mg of3-(dimethylamino)-1-propylamine-functionalized poly(methylmethacrylate-co-styrene) (40 mol % styrene, MW=100,000-150,000) wasdissolved in 1.903 g 3:3:3:1 v/v methyl ethylketone:toluene:xylenes:ethanol. The addition of 0.107 g water (to give a˜19:1 organic:H₂O w/w solution) caused some polymer to precipitate outof solution. The initial water content of the mixture was approximately53,000 ppm; however the actual amount of water dissolved into theorganic solvent resulted in organic solution with a water content of˜17,000 ppm. This vial was capped with a rubber septum. A single narrowgauge steel needle was inserted through the septum into the solution. Asecond needle was inserted into the septum, but not into the solution,to act as a gas outlet. CO₂ was introduced into the solution through thefirst needle at a flow rate of ˜10-20 mL min⁻¹ for 60 minutes whilestirring. After 60 minutes, the needles were withdrawn and the vial wassealed and left to sit for 24 hours.

After 24 hours, the liquid was decanted off from the polymer and thewater content was analyzed by Karl-Fischer titration. The firstsolution, the blank, was found to have a water content of roughly 16,600ppm, resulting in ˜2% of the water being removed via the polymer. Thesolution from the 2^(nd) vial had a water content of 13,800 ppm,resulting in a ˜19% removal of water by the polymer with CO₂ treatment.

The polymer was dried for 18 hours in a 140° C. oven and weighed todetermine the amount of polymer that did not precipitate duringtreatment and is thus lost. The blank was found to have lost 22% of theoriginal polymer mass and the CO₂-treated solution lost 46% of theoriginal polymer.

26.4 Dehydration of Isobutanol with a Polymer and Recycling of thePolymer

Isobutanol was purchased from Sigma Aldrich, Oakville and CO₂ was fromPraxair, Belleville. Water content was determined on a Mettler-ToledoC20 coulometric Karl-Fischer titrator using a Hydranal Coulomat AKsolution from Sigma Aldrich, Oakville.

In a glass vial container a stirbar, 28.0 mg of3-(dimethylamino)-1-propylamine-functionalized poly(methylmethacrylate-co-styrene) (40 mol % styrene, MW=100,000-150,000) wasdissolved in 4.546 g isobutanol and 0.509 g H₂O. The initial watercontent of the solution was 100,700 ppm. This vial was capped with arubber septum. A single narrow gauge steel needle was inserted throughthe septum into the solution. A second needle was inserted into theseptum, but not into the solution, to act as a gas outlet. CO₂ wasintroduced into the solution through the first needle at a flow rate of˜10-20 mL min⁻¹ for 60 minutes while stirring at which point solidsbegan to precipitate. After 60 minutes, the needles were withdrawn andthe liquid was decanted off. The water content was analyzed byKarl-Fischer titration and found to be 92,000 ppm, a roughly 9%reduction in water content.

The precipitated polymer was dried for 18 hours in a 80° C. oven. Thesolid was then weighed and it was found that approximately 50% was lostduring the 1^(st) cycle. The remaining polymer was redissolved in 2.274g of isobutanol and 0.265 g H₂O. The water content was 104,400 ppm. Themixture underwent a CO₂-treatment similar to the procedure outlinedabove. Once again the polymer precipitated during CO₂ treatment. Theliquid was decanted off and the water content was found to be 95,000ppm, representing an approximately 9% decrease in water content on the2^(nd) cycle.

26.5 Dehydration of a Mixed Organic Solvent with a Polymer withRecycling of the Polymer

Toluene and xylenes were purchased from Fisher Scientific, Ottawa.Silica and methyl ethyl ketone were purchased from Sigma Aldrich,Oakville. Ethanol was from Commerical Alcohols, Brampton and CO₂ fromPraxair, Belleville. Water content was determined on a Mettler-ToledoC20 coulometric Karl-Fischer titrator using a Hydranal Coulomat AKsolution from Sigma Aldrich, Oakville.

In a glass vial containing a stirbar, 25.8 mg of3-(dimethylamino)-1-propylamine-functionalized poly(methylmethacrylate-co-styrene) (40 mol % styrene, MW=100,000-150,000) wasdissolved in 1.951 g 3:3:3:1 v/v methyl ethylketone:toluene:xylenes:ethanol. The addition of 0.107 g water (to give a˜19:1 organic:H₂O w/w solution) caused some polymer to precipitate outof solution. The initial water content of the mixture was 50,100 ppm;however the actual amount of water dissolved into the organic solventresulted in organic solution with a water content of ˜17,000 ppm. Thisvial was capped with a rubber septum. A single narrow gauge steel needlewas inserted through the septum into the solution. A second needle wasinserted into the septum, but not into the solution, to act as a gasoutlet. CO₂ was introduced into the solution through the first needle ata flow rate of ˜10-20 mL min⁻¹ for 60 minutes while stirring wheresolids continued to precipitate. After 60 minutes, the needles werewithdrawn and the liquid was decanted off. The water content wasanalyzed by Karl-Fischer titration and found to be 15,900 ppm, a roughly6% reduction in water content.

The precipitated polymer was dried for 18 hours at 80° C. The solid wasthen weighed and it was found approximately 26% was lost during the1^(st) cycle. The remaining polymer was redissolved in 1.900 g of3:3:3:1 v/v methyl ethyl ketone:toluene:xylenes:ethanol. The addition of0.096 g water (to give a ˜19:1 Org:H₂O w/w solution) caused some polymerto precipitate out of solution. The water content of the mixture was48,100 ppm; however, the actual amount of water dissolved into theorganic solvent resulted in organic solution with a water content of˜17,000 ppm. The mixture underwent a CO₂-treatment similar to theprocedure outlined above. Once again, more polymer precipitated duringCO₂ treatment. The liquid was decanted off and the water content wasfound to be 11,900 ppm, representing a ˜30% decrease in water content onthe 2^(nd) cycle.

Example 27 Clay Settling with Switchable Water Additives

Montmorillonite (bentonite) from Panther Creek, Colo., USA was purchasedfrom Ward's Natural Science. Kaolinite (China Clay) from Panther Creek,Colo., USA was purchased from Ward's Natural Science.

In this study an equal amount of polyamine was placed into two different250 mL round bottom flasks equipped with a 2 cm Teflon stir-bar. 100 mLdeionized water was added and the solutions were stirred (600 rpm) untilthe polymer dissolved (10 min to 16 h). Then 1 g of Montmorillonite wasadded. Both suspensions were stirred at 600 rpm for 1 h, while CO₂ wasbubbled through one of the solutions using a gas dispersion tube. Afterthat, both suspensions were transferred into 100 mL graduated cylindersand the settling rate was monitored over time. After 16 hours samples ofboth supernatants were taken and the turbidity was measured on aOrbeco-Hellige TB200 turbidity meter. The range of the instrument is0-1100 NTU.

27.1 Butylated Polyethyleneimine (BPEI), MW=600

27.1.1 Butylated Polyethyleneimine (BPEI), MW=600 Low Concentration

Thirty-six milligrams of BPEI, MW=600 were used in the method set outabove. As shown in FIGS. 23A and 23B, the clay settles both with andwithout CO₂ present, with a faster settling rate without CO₂ present.Importantly, however, in the presence of CO₂ the supernatant was lessturbid.

27.1.2 Butylated Polyethyleneimine (BPEI), MW=600 High Concentration

Seventy-eight milligrams of BPEI, MW=600 were used in the method set outabove. The presence of CO₂ caused the clay to flocculate on top as avoluminous layer (40%) leaving a clear phase behind (see FIG. 24).Without CO₂ the clay settled slowly with a turbid supernatant after 16hour settling time.

lower clear layer supernatant without CO₂ with CO₂ Turbidity (after 16h) 390 NTU 11 NTU

Propylated Polyethyleneimine (PPEI) MW=600

Fifty-six milligrams of PPEI, MW=600 were used in the method set outabove. The clay settles both with and without CO₂ present, with a fastersettling rate with CO₂ present. However, the clay becomes veryvoluminous and settles only to 59% of the starting value after 24 h.Supernatant is clearer in the presence of CO₂.

lower clear layer supernatant without CO₂ with CO₂ Turbidity (after 2 h)263 NTU 4 NTU

27.2 3-(Dimethylamino)-1-Propylamine Functionalized PMMA (MW=120,000)

Forty six milligrams of 3-(dimethylamino)-1-propylamine functionalizedPMMA (MW=120,000) was used in the method set out above. The settling wasslightly faster without CO₂ present (see, FIG. 25). During the settlingprocess, the supernatant was less turbid in the presence of CO₂. Theturbidity measurement was taken after 2 hours.

supernatant without CO₂ supernatant with CO₂ Turbidity (after 2 h) 371NTU 6 NTU

27.3 3-(Dimethylamino)-1-Propylamine Functionalized PMMA/PS (10 Mol %Styrene, MW=10,600-15,900)

Forty three milligrams of 3-(dimethylamino)-1-propylamine functionalizedPMMA/PS (10 mol % styrene, MW=10,600-15,900) was used in the method setout above. Without CO₂ bulk settling is impossible to observe due tohigh turbidity of supernatant. With CO₂ settling is slow but producesvery clear supernatant. See FIGS. 26A and 26B.

supernatant without CO₂ supernatant with CO₂ Turbidity (after 16 h) 1100NTU 10 NTU

27.5 3-(Dimethylamino)-1-Propylamine Functionalized PMMA (MW=120,000)

Forty nine milligrams of 3-(dimethylamino)-1-propylamine functionalizedPMMA (MW=120,000) was used in the method set out above with themodification that 1 g kaolinite was used instead of montmorillonite.Instantaneous bulk settling was observed in the presence of CO₂ leavinga slightly turbid supernatant behind, which cleared out over 2 hours.See FIG. 27. Without CO₂ fast bulk settling was observed, however, thesupernatant was very turbid.

supernatant without CO₂ supernatant with CO₂ Turbidity (after 2 h) 1100NTU 25 NTU

3-(Dimethylamino)-1-Propylamine Functionalized PMMA (MW=350,000)

Forty nine milligrams of 3-(dimethylamino)-1-propylamine functionalizedPMMA (MW=350,000) was used in the method set out above with themodification of 2 g kaolinite being used instead of montmorillonite.Very fast bulk settling was observed both in the presence and absence ofCO₂. Supernatant less turbid with CO₂.

supernatant without CO₂ supernatant with CO₂ Turbidity (after 2 h) 1100NTU 28 NTU

Neutral 3-(Dimethylamino)-1-Propylamine Functionalized PAA (MW=50,000)

Fifty milligrams of neutral 3-(dimethylamino)-1-propylaminefunctionalized PAA (MW=50,000) was used in the method set out above.Without CO₂ bulk settling is slower and supernatant more turbid thanwith CO₂.

supernatant without CO₂ supernatant with CO₂ Turbidity (after 2 h) 62NTU 1 NTU

Study Using Hydrochloric Acid and 3-(Dimethylamino)-1-PropylamineFunctionalized PMMA MW=120,000

Fifty milligrams of 3-(dimethylamino)-1-propylamine functionalized PMMA(MW=120,000) was used in the method set out above. To one of thesuspensions, 45 μL of 4 M hydrochloric acid was added as opposed toacidifying the water by bubbling with carbon dioxide used previously.Both suspensions were stirred for 30 min, then transferred to graduatedcylinders and the settling monitored over time. In the presence ofhydrochloric acid, the settling was slightly faster and the supernatantslightly clearer than without the acid.

supernatant without acid supernatant with acid Turbidity (after 2 h) 23NTU 5 NTU

Study Using Sulfuric Acid and 3-(Dimethylamino)-1-PropylamineFunctionalized PMMA MW=120,000

Fifty milligrams of 3-(dimethylamino)-1-propylamine functionalized PMMA(MW=120,000) was used in the method set out above. To one of thesuspensions, 180 μL of 1 M sulfuric acid was added as opposed toacidifying the water by bubbling with carbon dioxide used previously.Both suspensions were stirred for 30 min, then transferred to graduatedcylinders and the settling monitored over time. In the presence ofsulfuric acid, the settling was very fast (47% of the starting heightafter 2 h) and the supernatant slightly clearer than without the acid.Settling in the absence of sulfuric acid was slow (79% of the startingheight after 2 h).

supernatant without acid supernatant with acid Turbidity (after 2 h) 25NTU 1 NTU

Study Using Formic Acid and 3-(Dimethylamino)-1-PropylamineFunctionalized PMMA MW=120,000

Fifty milligrams of 3-(dimethylamino)-1-propylamine functionalized PMMA(MW=120,000) was used in the method set out above. To one of thesuspensions, 1.8 mL of 0.1 M formic acid was added as opposed toacidifying the water by bubbling with carbon dioxide used previously.Both suspensions were stirred for 30 min, then transferred to graduatedcylinders and the settling monitored over time. In the presence offormic acid, the settling was very fast (33% of the starting heightafter 2 h) but the supernatant more turbid than without the acid.Settling in the absence of formic was slow (74% of the starting heightafter 2 h).

supernatant without acid supernatant with acid Turbidity (after 2 h) 24NTU 116 NTU

27.6 Control Experiment Using Polyacrylamide, MW=6,000,000

Thirty-one milligrams of polyacrylamide, MW=6,000,000 was used in themethod set out above. Very fast settling rates were observed both in thepresent and absence of CO₂ leaving very clear supernatants behind (seeFIGS. 28A and 28B). In the presence of CO₂ some clay particles wereobserved floating on top and in the supernatant.

supernatant without CO₂ supernatant with CO₂ Turbidity (after 16 h) 20NTU 27 NTU

Example 28 Osmotic Pressure Effects of Switchable Water Additives

Formation of ionic species in the presence of switchable water additivesand suitable trigger(s) leads to an increase in osmotic pressure due toan increase in higher unit solute concentrations.

The switchable osmotic pressure measurements were conducted on aZimm-Meyerson osmometer using Sterlitech UTC-80LB toray flat sheetmembranes. A 0.1% (w/v) switchable polyamine solution in water was madeby dissolving 20 mg of the corresponding polyamine in 20 mL deionizedH₂O. After the polyamine was completely dissolved, 13 mL of the solutionwas transferred into the glass cell of the osmometer and the outer glasscell was filled with deionized water. The system was closed with a lidand allowed to reach equilibrium overnight. Measurements of thecapillary tube and the control capillary were taken. The draw solutionwas then taken out of the cell and transferred into a graduatedcylinder. Both the draw solution and the solution of the outer cell werecarbonated by bubbling CO₂ with a gas dispersion tube for 1 h. The drawsolution was transferred back into the glass cell of the osmometer, thesystem was closed and held under an atmosphere of CO₂. A constant flowof CO₂ was maintained using two gauche needles, one of them connected toa CO₂ source with a flow rate of 10 ml/min. The heights taken wereheight differences of the capillary tube connected to the cell and thecontrol capillary tube. Based on these heights the hydrostatic pressurewas calculated using the equation:

Π=ρhg

where Π is the hydrostatic pressure, ρ is the density of the solution, his the height of the water column and g is the force of gravity.Hydrostatic pressure is taken to be proportional to osmotic pressure ofthe solution at equilibrium.

28.1 Switchable Osmotic Pressure Experiment Using BPEI, MW=600

Twenty-eight milligrams of BPEI was suspended in 20 mL of deionizedwater. Height measurements were taken before and after CO₂ treatment.

hydrostatic pres- hydrostatic pressure sure without CO₂ pressure withCO₂ increase BPEI, MW = 600 363 Pa 2433 Pa 6.7

28.2 Switchable Osmotic Pressure Experiment Using BPEI, MW=10,000

Twenty-seven milligrams of BPEI was suspended in 25 mL of deionizedwater. Height measurements were taken before and after CO₂ treatment.

hydrostatic pres- hydrostatic pressure sure without CO₂ pressure withCO₂ increase BPEI, MW = 10,000 88 Pa 618 Pa 7.0

28.3 Switchable Osmotic Pressure Experiment Using Ionic PAA(MW=450,000):

Twenty-milligrams of ionic PAA (MW=450,000) with3-(dimethylamino)-1-propylammonium counterion were dissolved in 20 mL ofdeionized water. Height measurements were taken before and after CO₂treatment.

hydrostatic pres- hydrostatic pressure sure without CO₂ pressure withCO₂ increase Ionic PAA 29 Pa 450 Pa 15.5 (MW = 450,000)

28.4 Switchable Osmotic Pressure Experiment Using3-(Dimethylamino)-1-Propylamine Functionalized PMMA (MW=120,000):

Forty-six milligrams of 3-(dimethylamino)-1-propylamine functionalizedPMMA (MW=120,000) were dissolved in 46 mL of deionized water. Heightmeasurements were taken before and after CO₂ treatment.

hydrostatic pres- hydrostatic pressure sure without CO₂ pressure withCO₂ increase functionalized 137 Pa 1923 Pa 14.0 PMMA (MW = 120,000)

28.5 Switchable Osmotic Pressure Experiment Using3-(Dimethylamino)-1-Propylamine Functionalized PMMA (MW=35,000):

Sixteen milligrams of 3-(dimethylamino)-1-propylamine functionalizedPMMA (MW=35,000) were dissolved in 48 mL of deionized water. Heightmeasurements were taken before and after CO₂ treatment.

hydrostatic pres- hydrostatic pressure sure without CO₂ pressure withCO₂ increase functionalized 412 Pa 1687 Pa 4.1 PMMA (MW = 35,000)

After treatment with CO₂ and measurement of osmotic pressure, thesolution was taken out of the osmometer and heated to 50° C. withnitrogen sparging for 6 hours. The hydrostatic pressure of the solutionwas then measured and found to be 638 Pa.

28.6 Switchable Osmotic Pressure Experiment Using3-(Dimethylamino)-1-Propylamine Functionalized PMMA/PS (1.4 Mol %Styrene, MW: 9,200-12,900)

12 mg of 3-(dimethylamino)-1-propylamine functionalized PMMA/PS (1.4 mol% styrene, MW: 9,200-12,900) were dissolved in 38 mLl of deionizedwater. Height measurements were taken before and after CO₂ treatment.

hydrostatic pres- hydrostatic pressure sure without CO₂ pressure withCO₂ increase functionalized 226 Pa 1403 Pa 6.0 PMMA/PS (1.4 mol %styrene)

28.7 Switchable Osmotic Pressure Experiment Using3-(Dimethylamino)-1-Propylamine Functionalized PMMA/PS (10 mol %Styrene, MW: 10,600-15,900)

13 mg of 3-(dimethylamino)-1-propylamine functionalized PMMA/PS (10 mol% styrene, MW: 10,600-15,900) were dissolved in 40 mL of deionizedwater. Height measurements were taken before and after CO₂ treatment.

hydrostatic pres- hydrostatic pressure sure without CO₂ pressure withCO₂ increase functionalized 118 Pa 1785 Pa 15.0 PMMA/PS (10 mol %styrene)

Switchable Osmotic Pressure Experiment Using Neutral3-(Dimethylamino)-1-Propylamine Functionalized PAA (MW=1,800)

Nine milligrams of 3-(dimethylamino)-1-propylamine functionalized PAA(MW=1,800) were dissolved in 36 mL of deionized water. Heightmeasurements were taken before and after CO₂ treatment.

hydrostatic pres- hydrostatic pressure sure without CO₂ pressure withCO₂ increase functionalized PAA 287 Pa 1579 Pa 5.5 (MW = 1,800)

Switchable Osmotic Pressure Experiment Using PDEAEMA (MW=55,000)

Fifty-four milligrams of PDEAEMA were dissolved in 54 mL of carbonatedwater. Height measurements were only taken of the carbonated solution,as the polymer was not soluble in non-carbonated water.

hydrostatic pres- hydrostatic pressure sure without CO₂ pressure withCO₂ increase PDEAEMA (MW = Not soluble 1957 Pa 55,000)

28.8 Switchable Osmotic Pressure Control Experiment UsingN,N-dimethylcyclohexylamine:

Forty-eight milligrams of N,N-dimethylcyclohexylamine were dissolved in21 mL of deionized water. Height measurements were taken before andafter CO₂ treatment.

hydrostatic pres- hydrostatic pressure sure with CO₂ pressure with CO₂increase N,N-dimeth- 580 Pa 1550 Pa 2.7 ylcyclohexylamine

28.9 Switchable Osmotic Pressure Control Experiment Using Polyacrylamide(MW=6,000,000):

Twenty milligrams of polyacrylamide were dissolved in 20 mL of deionizedwater. Height measurements were taken before and after CO₂ treatment.

hydrostatic pres- hydrostatic pressure sure with CO₂ pressure with CO₂increase polyacrylamide 98.1 Pa 176 Pa 1.8 (MW = 6,000,000)

As demonstrated using polyacrylamide, only a very small change inpressure can be achieved by the addition of CO₂ in the absence of aswitchable additive. Further, the switchable tertiary amine tested in28.8 was capable of generating a lower change in osmotic pressure thanthe polyamines, but more than observed for polyacrylamide.

Example 29 Homogenous Catalysis Using Switchable Water Additives

Homogeneous catalysts are often more active and selective thanheterogeneous catalysts but are far more difficult to separate from theproduct. The development of means to separate, recover, and recyclehomogeneous catalysts is an important area of research for both industryand academia (Catalyst Separation, Recovery and Recycling: Chemistry andProcess Design, D. J. Cole-Hamilton, R. Tooze, Eds., Springer,Dordrecht, 2006; M. J. Muldoon, Dalton Trans., 2010, 39, 337). Oneapproach, already industrialized in a few cases, is catalysis in abiphasic mixture of two solvents (B. Cornils, E. G. Kuntz, Aqueous-PhaseOrganometallic Catalysis 2nd ed., B. Cornils, W. G. Hermann, Eds.,Wiley-VCH, Weinheim, 2004; U. Hintermair, W. Leitner, P. G. Jessop,Supercritical Solvents, W. Leitner, P. G. Jessop, Eds., Wiley/VCHWeinheim, 2010). Such reactions involve the dissolution of a catalystinto one of the solvents and the dissolution of the reagents into theother solvent. The small partitioning of the reagent into the solventcontaining the catalyst allows the reaction to proceed. Aqueous/organicbiphasic systems are of great interest and are currently in use for theindustrial hydroformylation of low carbon number-containing alkenes (B.Cornils, E. G. Kuntz, Aqueous-Phase Organometallic Catalysis 2nd ed., B.Cornils, W. G. Hermann, Eds., Wiley-VCH, Weinheim, 2004). These systemsoften utilize transition metals ligated by sulfonated phosphines toincrease the water solubility of the metal, causing the catalyst toreside in the aqueous phase. After the reaction is completed, theproduct (organic) phase is decanted and the aqueous catalyst-containingphase is used again.

Aqueous/organic biphasic catalysis of this type has both advantages anddisadvantages. An advantage of this method is, of course, the easyseparation of catalyst from product. A key disadvantage is the slow rateof reaction that results from the catalyst and the reactants being intwo different phases, especially when the reactant (such as 1-octene orstyrene) has very poor solubility in water. One solution to this problemis to design a trigger to make the aqueous and organic phases merge intoone phase during the catalysis and then to separate into two phasesagain after the reaction is complete. This can be accomplished usinghigh pressure CO₂ as a trigger (THF and water are miscible when highpressure CO₂ is absent and form two liquid phases when high pressure CO₂is present) (J. Lu, M. L. Lazzaroni, J. P. Hallet, A. S. Bommarius, C.L. Liotta, C. A. Eckert, Ind. Eng. Chem. Res., 2004, 43, 1586). Thepresent example provides a method for achieving the same result usingonly 1 atm of CO₂.

A switch of miscibility for organic solvents in water can provide anorganic/aqueous mixture of solvents that is monophasic duringhomogeneous catalysis and then switched to biphasic by the introductionof CO₂ after the catalysis is complete. The process involves homogeneouscatalysis (such as hydroformylation of an alkene) in a water/organicsolvent monophasic mixture that also contains a small amount of asoluble amine (FIG. 29). After the catalysis is complete, CO₂ is addedreacting with the amine, causing a rise in the ionic strength of thesolution and thereby triggering the salting out of both the organicsolvent and the product from the aqueous phase. If a suitablyhydrophilic catalyst is selected, the catalyst remains in the aqueousphase isolated from the products or reaction. After decantation of theproduct phase, the removal of CO₂ from the water regenerates a low ionicstrength aqueous phase that can accept fresh reagents and THF and thereaction can be repeated.

The hydroformylation of styrene is an attractive model system becauseits aldehyde products have potential use in pharmaceutical and finechemical production and its water solubility is low (CRC Handbook ofChemistry and Physics, 79^(th) ed. D. R. Lide, Ed., CRC Press, BocaRaton, 1998), which make a traditional aqueous/organic biphasic reactioninefficient. Our other examples of switchable water showed that THFcould easily be forced out of aqueous solution with the application ofCO₂. Our initial studies into hydroformylation of styrene found thatthis weakly coordinating organic solvent may hinder the hydroformylationreaction. We therefore searched for other water-miscible organicsolvents that could solubilize styrene and could also be salted out by aswitchable water additive in the presence of CO₂, and found thattert-butanol is one appropriate organic solvent choice.

Styrene Hydroformylation in the Presence of Switchable Water Additive:

To a 10 mL 3:2 t-BuOH:H₂O (v/v) mixture, 0.5 g N,N-dimethylethanolamine(DMEA) was added as the amine additive to create a 1.4 molal solution(relative to water). Styrene (0.15 mL), [Rh(COD)Cl]₂, and TPPTS wereadded (Rh=0.5 mol % relative to styrene, P/Rh=7, COD=cyclooctadiene,TPPTS=tris(3-sulfophenyl)phosphine trisodium salt hydrate). Thisgenerated a single phase pale yellow solution (FIG. 30, top left). Thesolution was transferred to a pressure vessel, heated to 100° C.,pressurized to 5 bar with synthesis gas (1:1 CO:H₂), and allowed toreact for 3 h. After the reaction, CO₂ was bubbled through the solution,generating a biphasic system with the catalyst residing in a darkred-brown aqueous phase and the product residing in the clear, colorlesst-BuOH phase. The organic phase was removed and analyzed. The aqueousphase was heated to 65° C. and N₂ was bubbled through it in order toremove the CO₂ and lower the ionic strength of the solution. Thisprocess changed the aqueous phase to a golden yellow colour. A freshsupply of t-BuOH, styrene, water (to account for some evaporation) andTPPTS (3 Rh equivalents for each cycle, which brought the final P/Rhratio to 13) was added. The catalysis and separation process wasperformed for three cycles, giving consistently high conversion, goodaldehyde selectivity and good regioselectivity towards the branchedisomer (see Entry 1 in the table below). By-products were identified asthe hydrogenated product, ethylbenzene, and acetophenone; the last ofthese forms through a completely different mechanism to thehydroformylation when advantageous molecular oxygen is present (rhodiumcan catalyze the oxidation reaction of terminal alkenes with molecularoxygen to give methyl ketones, see: (a) H. Mimoun, M. P. Machirant, I.S. de Roch, J. Am. Chem. Soc., 1977, 100, 5437. (b) O. Bortolini, F. diFuria, G. Modena, R. Seraglia, J. Mol. Cat., 1984, 22, 313. (c) G. A.Olah, Á. Molnár, Hydrocarbon Chemistry 2^(nd) ed.; John Wiley and Sons,Hoboken, 2003).

It was found that the addition of more TPPTS through each cycle wasnecessary to maintain good conversions and selectivities. Withoutadditional TPPTS added before each addition of fresh reactant, theaqueous phase progressively darkened through the cycles and blackprecipitate formed. Conversions then decreased sharply through thecycles (see Entry 2 in the table below). Without wishing to be bound bytheory, the likely cause of these observations is oxidation of TPPTS,deactivating the catalyst. Even under stringent oxygen-free conditions(see Entry 3 in the table below), the addition of additional TPPTS wasnecessary as conversions eventually decreased upon recycling, althoughthe aldehyde selectivity was improved compared to Entry 1 below wherethe recycling processes were carried out in air.

Cycle 1 Cycle 2 Cycle 3 % Conversion/% % Conversion/% % Conversion/%Additive Aldehyde Selectivity B/L Aldehyde Selectivity B/L AldehydeSelectivity B/L DMEA ^(b) 98.9/96.1 8.0 99.4/89.3 6.8 97.2/97.0 6.5 DMEA^(c) 98.5/91.1 8.8 87.9/87.7 6.3 40.7/88.5 5.3 DMEA ^(d) 95.3/98.9 8.896.3/99.0 6.5 73.7/98.1 5.7 TMDAB ^(c, e) 85.2/87.7 7.7 43.8/87.3 5.4 8.9/85.2 4.6 ^(a) Conditions: Reaction mixture was comprising 6 mLtert-butanol, 4 mL H₂O, 1.4 molal of an amine additive, 0.25 mol %catalyst, and 7:1 P:Rh. Reaction was run at 100° C. at 5 bar syn gas(1:1 CO:H₂) for 3 hours. Yields were determined by GC with theassistance of previously-prepared calibration curves. ^(b) Average oftwo runs, 3 equivalents of TPPTS in regard to Rh added during each cyclefor a final ratio of 13:1 P:Rh. ^(c) No phosphine added duringrecycling. ^(d) Solvents degassed and kept under N₂, CO₂ or CO/H₂ at alltimes, no phosphine added during recycling. ^(e) 0.8 molal additiveadded.

The retention of the DMEA in the aqueous phase upon protonation by CO₂was not complete and loss of DMEA to the product phase in each cycle mayaccount for the changing volumes of aqueous phase in successive cycles(FIG. 30, right side images). To minimize loss of the amine to theorganic phase, it may be preferable to use polyamines as additives; theygenerally have better retention in the aqueous phase and can generatesolutions of greater ionic strength at lower loadings. However, apolyamine that does not interfere with the reaction should be selected.The conversions observed during hydroformylation of styrene whenN,N,N′,N′-tetramethyl-1,4-diaminobutane (TMDAB) was used (see Entry 4above), while effective, were lower than observed using DMEA. Withoutwishing to be bound by theory, this may be the a result of the bidentatenature of the TMDAB, which may be competing with TPPTS for positions onthe metal, ultimately deactivating the catalyst. The use of betterchelating water-soluble phosphines may improve conversions using thepolyamine switchable water additives without the resulting loss ofcatalytic activity.

The leaching of rhodium metal into the organic product phase wasobserved by ICP-MS (see the table below). Minimal leaching was observedthrough the first cycle; however upon the second and third cycles, theamount of rhodium lost to the product phase did increase. Despite theincreases in rhodium leaching as recycling of the aqueous phaseproceeded, the greatest amount of total loss in a single recycling stepwas never more than roughly 10% of the original amount of rhodiuminitially used.

The table below shows the concentration of rhodium found in the organicphase, containing products, after separation by switchable water asdetermined by ICP-MS. Samples were acquired from organic phases noted inEntry 1 of the table above.

Rhodium Concentrations in the Organic Phases^(a) Cycle 1 Cycle 2 Cycle 31.07 ± 0.04 mg L⁻¹ 3.63 ± 0.04 mg L⁻¹ 10.12 ± 0.25 mg⁻¹ L ^(a)Average oftwo runs.

This example demonstrates the successful use of switchable wateradditives to allow homogeneous catalysis to take place in a monophasicsolvent mixture and yet allow the subsequent catalyst/product separationto take place in a biphasic solvent mixture. This method does not sufferfrom the traditional mass transfer issues that accompany biphasicreactions because the system is monophasic during the catalysis. Thismethod can also tolerate alkenes of lower water solubility thantraditional biphasic aqueous/organic catalysis. The hydroformylationreactions performed in switchable water are run at low syn gaspressures, on short timescales, and with facile separation of catalystfrom product because of CO₂ induced phase separation. Recycling of thecatalyst solution was performed with ease by removing CO₂ from thesolution by sparging with an inert gas or air and/or moderate heating.The Rh/TPPTS catalyst maintained good conversion, product selectivity,and regioselectivity after recycling. This method for solving theinherent rate limitations of conventional biphasic catalysis does notrequire high pressure CO₂ or expensive fluorous or ionic liquidsolvents.

Example 30 Solubility of Switchable Water Additives

30.1 Switchable Solubility of Butylated Polyethyleneimine (MW=600)

In a 100 mL round bottom flask equipped with a 1 cm stir-bar, 293 mg ofbutylated polyethyleneimine (MW=600) was suspended in 50 mL deionizedwater and stirred for 30 min at room temperature. The solid was allowedto settle for 72 h, then 5 mL of the supernatant was removed andfiltered. From the filtered solution, three samples of 1 mL each wereplaced into round bottom flasks. The water was evaporated and thesamples weighed. An average of all three sample weights was taken.

The rest of the solution was treated with CO₂ for 1 hour by bubblingwith a single gauge needle (flow rate: 80 ml/min). The mixture turnedalmost completely clear but some BPEI was still insoluble, hencesaturated. Twenty millilitres of the solution was filtered off and threesamples of 5 mL each were placed into round bottom flasks. The water wasevaporated and the samples weighed. An average of all three samples wastaken. An overview of the results is given below.

sample 1 sample 2 sample 3 average solubility 0.33 mg/mL 0.33 mg/mL 0.33mg/mL 0.33 mg/mL without CO₂ solubility  7.2 mg/mL  7.8 mg/mL  8.4 mg/mL 7.8 mg/mL with CO₂

Replacing CO₂ with argon lead to the formation of a white suspension.Another addition of CO₂ dissolved the polymer again. This process wasrepeated 3 times.

30.2 Switchable Solubility of Propylated Polyethyleneimine (MW=600)

In a 100 mL round bottom flask equipped with a 1 cm stir-bar, 293 mg ofpropylated polyethyleneimine (MW=600) was suspended in 50 mL deionizedwater and stirred for 30 min at room temperature. The solid was allowedto settle for 72 h, then 10 mL of the supernatant was removed andfiltered. From the filtered sample, three samples of 3 mL each wereplaced into round bottom flasks. The water was evaporated and thesamples weighed. An average of all three samples was taken.

The rest of the solution was treated with CO₂ for 1 hour by bubblingwith a single gauge needle (flow rate: 80 ml/min). The mixture turnedcompletely clear, hence it was below saturation point. 10 mL of thesolution was filtered off and three samples of 3 mL each were placedinto round bottom flasks. The water was evaporated and the samplesweighed. An average of all three samples was taken. An overview of theresults is given below.

sample 1 sample 2 sample 3 average solubility  3.3 mg/mL  3.3 mg/mL  3.6mg/mL  3.5 mg/mL without CO₂ solubility 72.0 mg/mL 72.0 mg/mL 73.0 mg/mL72.3 mg/mL with CO₂

As all of the polymer dissolved in the presence of CO₂, the actualsolubility was higher than 72.3 mg/mL.

Replacing CO₂ with argon lead to formation of a white suspension.Another addition of CO₂ dissolved the polymer again. This process wasrepeated 3 times.

Example 31 Switchable Water Additive Conductivity Measurements

Solution conductivity measurements were recorded on a Thermo ScientificOrion 5-Star Plus conductivity meter (Fisher Scientific, Ottawa,Ontario, Canada). Ultra pure water (18 MΩ) was obtained using an ElgaLab Water PureLab Flex system (High Wycombe, UK). Tetra-n-butylammoniumbromide was purchased from Sigma Aldrich Inc. (Oakville, Ontario,Canada). 3-dimethylamino-1-propylamine was purchased from Alfa Aesar(VWR, Mississauga, Ontario, Canada).

The solution conductivities of the materials given below were measured.The mass of each material indicated was weighed into a 150 mL beakercharged with a stir bar along with 100 mL of ultra pure water. Thesolutions were stirred until visibly dissolved and their conductivitymeasured. In the case of both MW=450,000 functionalized and ionicpolyacrylic acid samples and the MW=350,000 polymethyl methacrylatesample, gel particles formed, indicating partial solubility. Allsolutions were left to stir overnight to test reproducibility. Solutionconductivities were re-recorded giving little change in values. CO₂ wasbubbled at 10 psi through a fine glass frit tube (to make bubble size assmall as possible for greater surface area and therefore fastercarbonation) with each solution for 30 minutes. In the case of TBAB andfunctionalized PMMA, significant amounts of bubbling were observed.Solution conductivities were re-recorded.

Initial C C after 30 mins Material Mass (g) (μS/cm) CO₂ (μS/cm)Ultrapure H₂O N/A 1.31 41.2 H₂N(CH₂)₃NMe₂ 0.255 398 3360 [^(n)Bu₄N]Br0.806 1892 1781 PAA(1,800) 0.180 235 238 Ionic PAA (MW = 1,800) 0.196398 1107 (1240)^(a) Ionic PAA 0.196 145 750 (MW = 450,000) NeutralFunctionalized 0.200 251 818 PAA (MW = 1,800) Neutral Functionalized0.200 58 334 PAA (MW = 50,000) Neutral Functionalized 0.200 2.07 42.4PAA (MW = 450,000)^(c) Functionalized PMMA 0.112 201 1086 (MW = 35,000)Functionalized PMMA 0.080^(b) 102 494 (MW = 120,000) Functionalized PMMA0.112 186 410 (MW = 350,000) ^(a)An aliquot of this solution after thismeasurement was sealed in a high pressure reactor, pressurized to 130psi, and stirred for 16 hours at room temperature before solutionconductivity measurement was re-measured. This measurement was performedto verify that the procedure described above (30 min, 10 psi CO₂bubbling) was sufficient to fully switch additive. ^(b)Measurementperformed in 80 mL deionized water. ^(c)This polymer sample was observedto have very low solubility in water.

Example 32 Kaolinite Clay Settling Using Switchable Water

Kaolinite clay fines constitute about half of the solid content in oilsands tailing (Ramachandra Rao, S., 1980, “Flocculation and dewateringof Alberta oil sands tailings.” Int. J. Miner. Process., 7 (3),245-253). Kaolinite, a hydrous aluminum silicate of compositionAl₂O₃.2Sio₂.2H₂O (Giese, R., & van Oss, C., 2002, Colloid and SurfaceProperties of Clays and Related Minerals (Vol. 105), A. Hubbard, Ed.United States of America: Marcel Dekker, Inc.; and Velde, B., 1995,Origin and Mineralogy of Clays. United States of America:Springer-Verlag New York, Inc.), occurs in roughly hexagonal plateletswith a length-to-thickness ratio of 10:1 (Michaels, A. a., 1962,“Settling Rates and Sediment Volumes of Flocculated Kaolin Suspensions.”Ind. Eng. Chem. Fundamen., 1 (1), 24-33). Due to the amphoteric propertyof kaolinite, the faces of the particles possess a permanent negativecharge, while the charge on the edge surface is pH-dependent. Underacidic conditions (pH lower than 6) (Michaels, 1962. supra), thealuminum exposed at the edges acquires hydrogen ions from water andassumes a positive charge. The edge and face surfaces then mutuallyattract, leading to edge-face (E-F) flocculation, and giving form to“card-house” flocs. Under alkaline conditions the edges become neutralor even positively charged, thus disrupting the E-F interactions,providing that electrolyte concentration is low. Increase in electrolyteconcentrations, and thus increase in ionic strength of the solution,reduces electrostatic interactions (attractive or repulsive) due tocompressed electrical double layer or ion shielding of surface charges.As a result, flocculation primarily occurs between basal surfaces—orface-face (F-F)—forming “card-pack” flocs. The ionic strength effect isindependent of solution pH. (Schofield, R., 1954, “Flocculation ofkaolinite due to the attraction of oppositely charged crystal faces”Discussions Faraday Soc., 18, 135-145; Michaels, 1962, supra; and Nasser& James, 2006, “Settling and sediment bed behaviour of kaolinite inaqueous media.” Separation and Purification Technology, 51 (1), 10-17).

In this example, the use of a switchable water additive as theflocculating agent is demonstrated. The use of a switchable wateradditive can enhance water recyclability in oil sands operations bydrastically reducing the energy and material demanded by conventionaltailing dewatering methods.

Experimental & Materials

Kaolinite Suspension Settling and Supernatant Turbidity

Two separate samples of kaolinite were purchased from Ward's NaturalScience and were used as received. Deionized water with a resistivity of18.2 MΩ·cm (Synergy® UV, Millipore) was used throughout this study. CO₂(Supercritical Chromatographic Grade, 99.998%, Praxair) was used asreceived. 100 mL graduated cylinders (Kimble Kimax, single metric scale,20025H 50) were used for all settling tests. TMDAB was purchased fromTCI. Consistency in cylinder dimensions is particularly important, as ithas been reported that container height can influence settling rate(Michaels, 1962, supra).

The kaolinite suspension was prepared by adding clay fines to 100 mL ofaqueous TMDAB. The effects of changing clay loadings (2.5%, 5%, and 7%w/v) and TMDAB concentrations (blank, 0.01, 0.1, 1, 10 mM) on settlingbehaviour were investigated. The mixture was stirred with a magneticstirrer for 15 minutes at 900 rpm prior to transfer to a graduatedcylinder. Both “on” (CO₂-treated) and “off” forms of TMDAB wereinvestigated for their effect on settling. For the “on” experiments, CO₂was bubbled through the mixture in the graduated cylinder using a20-gauge needle for 1 hour at 100-150 mL/min. The cylinder was thenimmediately sealed with a rubber septum and bulk settling was monitoredover 2 hours with a cathetometer (Eberbach). Supernatant from each ofthe settling experiments was sampled and its turbidity was measuredusing a turbidity meter (TB200, Orbeco-Hellige).

Settling Tests to Investigate the Effect of pH and Ionic Strength

The pH of the following 5% (w/v) kaolinite suspensions were measured:CO₂ blank and 1 mM TMDAB and 10 mM TMDAB after CO₂-treatment. Toinvestigate the effect of pH on suspension settling behaviour, 5% (w/v)kaolinite suspensions were prepared, and the pH of each suspension wasadjusted with HCl and NaOH to match the pH of corresponding treatmentconditions. To investigate the effect of ionic strength on suspensionsettling behaviour, pH was again corrected to match the pH ofcorresponding treatment conditions, and ionic strength was adjusted withNaCl or ammonium sulphate, assuming all basic sites on the diamine wereprotonated.

Particle Size and Zeta Potential Measurements

Particle size and zeta potential were measured using Zetasizer Nano ZS(Malvern). 25 mg of clay fines (kaolinite and montmorillonite) wereadded to 10 mL of deionized water. A suspension was created using avortex. All CO₂ treatments were conducted for 1 hour. The pH wasadjusted with HCl and NaOH.

Results & Discussion

The Effect of TMDAB on Kaolinite Suspension Behaviour

Kaolinite and montmorillonite clays fines naturally form a stableaqueous colloidal suspension. The presence of TMDAB in suspension in the“off” form did not have any observable effect on particle flocculationand settling and maintained a stable suspension. However, uponintroduction of CO₂ to turn on TMDAB, settling was observed in aconcentration-dependent manner, as presented in FIG. 31. The settlingprofiles are plotted as the percent column height of the interfacialplane between the slurry and the supernatant as a function of time.Increasing TMDAB concentration lead to slower settling rates. The upperlimit of settling rate was characterized by a CO₂-treated suspensionwith no TMDAB. At 0.1 mM and 0.01 mM TMDAB (not shown) the settlingprofiles were not different from that of the CO₂-treated suspensionwithout additive. CO₂ alone can facilitate bulk settling in a claycolloid. In fact, it is already an industrial practice of CanadianNatural Resources Limited to inject CO₂ into tailing ponds to acceleratethe settling of tailing fines. CO₂ forms carbonic acid in water andthereby lowers the pH. Low pH promotes clay particle flocculation andthe subsequent settling.

While settling rate was the most rapid in a CO₂-treated suspensionwithout TMDAB, it resulted in the most turbid supernatant; as theconcentration of TMDAB increased, the turbidity of the supernatantdecreased (FIG. 32). However, at high concentrations (100 mM), thepresence of oxidized amine became significant and imparted a yellowishtinge in the supernatant. Thus, an important design consideration is acompromise between desirable settling rate and acceptable waterturbidity. 1 mM TMDAB was required to reduce the supernatant turbidityby a significant amount. A photographic time-profile of the settling ofa kaolinite suspension treated with 10 mM TMDAB and CO₂ is presented inFIG. 33. The clarity in the supernatant and the sharp sediment linesuggest that flocs were formed with comparable size and density(Michaels, 1962, supra). FIG. 34 illustrates the supernatant turbidityat different treatment conditions and colouration at 100 mM TMDAB.

Zeta potential is a simple method to predict colloidal system stability(Delgado, A., González-Caballero, F., R. Hunter, L. K., & Lyklema, J.(2005). Measurement and Interpretation of Electrokinetic Phenomena. PureAppl. Chem., 77 (10), 1753-1805). At large absolute zeta potentialvalues, the particles are highly charged and repel one another. Thisprevents the particles from flocculating, and thus results in a stablesuspension. Flocculation begins to take place at a critical value around−30 mV. (Everett, D. (1988). Basic Principles of Colloid Science.London, England: Royal Soceity of Chemistry) The closer zeta potentialis to zero, the more it indicates weakened repulsive forces, whichallows the particles to flocculate under attractive van der Waalsforces. FIG. 35 shows the zeta potentials of clay particles underdifferent treatment conditions. A kaolinite colloid without treatment orwith the “off” form of TMDAB generally exhibited zeta potential valuesin the stable range. This was consistent with the suspension settlingexperiments, as no settling was observed under these two conditions. Thezeta potential of a CO₂-treated suspension with no additives indicatedsome flocculation and destabilization of the system; however, only to aminimal extent. This was also consistent with the settling test: whilesettling did occur, the supernatant was turbid. The “on” form of 1 mMTMDAB was able to significantly lower the zeta potential of thesuspension components. This was once again reflected in the settling ofclay and a much clearer supernatant.

Aggregate size can serve as an indication of flocculation. Whileaggregate size is not a fundamental property of a flocculatedsuspension, it is a dynamic property of the effective collisions thatcontribute to aggregation (Michaels, 1962, supra). FIG. 36 illustratesthat particle size measurements exhibited a similar trend to zetapotential measurements under the same set of treatment conditions. Nonotable increase in particle size was evident in the presence of the“off” form of TMDAB or even under CO₂ treatment. However, the particlesize in the TMDAB-CO₂ treated suspension was approximately double thatof the suspension particles under no treatment. Particle size is only acrude indication of flocculation, since naturally occurring clayparticles exhibit a wide range of sizes, as indicated by the PDI ofthese samples.

The Effect of Clay Loading on Kaolinite Suspension Settling Behaviour

Kaolinite clay loading level can influence the suspension settlingcharacteristics. Settling rate decreased as clay loading increased, asshown in FIG. 37. This was consistent with the findings reported byMichaels and Bolger (Michaels, 1962, supra). The supernatant turbiditywas also sensitive to clay loading in CO₂-treated suspensions: turbidityincreased significantly with increasing clay loading (FIG. 38). However,this loading-dependent effect on turbidity was not observed insuspensions treated with 1 mM TMDAB and CO₂. TMDAB exerted a muchstronger effect on clay behavior in suspension, which overcame theinfluence of clay loading level.

The Effect of pH and Ionic Strength on Kaolinite Suspension Behaviour

To investigate whether the TMDAB-induced effect on kaolinite suspensionwas predominately driven by solution pH effect or ionic strength effect,settling tests were conducted with suspensions adjusted to have pHand/or ionic strength that corresponded to CO₂-treated TMDABsuspensions. All pH and ionic strength suspension settling tests wereconducted with kaolinite sample 2 (see below).

The pH of kaolinite suspensions under different treatment conditions wasmeasured and shown in Table A. Kaolinite clay particles were shown tohave acidic properties in an aqueous environment. Three suspensions wereeach adjusted to have the same pH as a suspension that was CO₂ treated(1), 1 mM TMDAB-CO₂ treated (2), or 10 mM TMDAB-CO₂ treated (3).Settling was observed in 1 and 2 but not 3. The bulk settling for 1 and2 exhibited comparable profiles. The supernatant turbidity of 2,however, was significantly higher than that of 1 (Table 2). Low pH wasfavourable for kaolinite flocculation. An increase in solution pH becameincreasingly unfavourable until settling was no longer observed.Michaels and Schofield had reported that under pH 6 kaolinite particlescould attract electrostatically and form “card-house” flocs. Thiselectrostatic attraction is lost with increasing pH. (Michaels, 1962,supra; and Schofield, R., 1954, “Flocculation of kaolinite due to theattraction of oppositely charged crystal faces.” Discussions FaradaySoc., 18, 135-145). While pH exerted an effect on suspension behavior,in particular supernatant turbidity, bulk-settling rate was independentof solution pH.

Zeta potentials of 1, 2, and 3 all measured below the critical value,with 3 being significantly higher.

TABLE A pH Sample 1 Sample 2 No treatment 5.35 4.90 CO₂ — 4.25 1 mMTMDAB — 7.13 1 mM TMDAB + CO₂ — 4.75 10 mM TMDAB — 10.41 10 mM TMDAB +CO₂ — 5.95

TABLE B Corresponding Supernatant turbidity Study pH treatment (NTU) 14.25 CO₂ Blank  64 2 4.75 1 mM TMDAB + CO₂ 520 3 5.95 10 mM TMDAB + CO₂NO SETTLING

TMDAB in its “off” form acted as a base and elevated suspension pH in aconcentration-dependent manner, as illustrated in Table A. Since it hasbeen shown that settling does not occur at high pH, it is reasonablethat no settling was observed in suspensions treated with the “off” formof TMDAB.

A discrepancy in supernatant turbidity was observed between the 2samples of kaolinite in suspensions treated with CO₂ in FIG. 32. Thesupernatant turbidity that resulted from sample 2 was significantlylower than that which resulted from sample 1 under the same treatmentcondition. Without wishing to be bound by theory, the discrepancy couldbe explained by the pH effect and differences in particle size. Sample 2was more acidic than sample 1 in an aqueous environment (Table A); thus,a suspension created with sample 2 treated with CO₂ was at a lower pHthan a suspension similarly created with sample 1. The difference in pHwas likely enough to result in the observed differences in supernatantturbidity. Furthermore, FIG. 36 indicates that sample 2 particle sizeswere on average larger than sample 1 particles. Larger particle sizeslead to more pronounced Van der Waals attractions and larger influenceby gravitational pull; thus, a suspension of larger particles settlesmore uniformly and rapidly.

While pH was found to influence the ability of clay particles to settle,the pH effect failed to explain why an increase in TMDAB concentrationlead to a decrease in both settling rate and turbidity. Ionic strength,another known factor in suspension settling, was investigated as apotential mechanism through which TMDAB works. For a given amineadditive (denoted B) with n basic sites, the fate of the aqueous aminein the presence of CO₂ is illustrated by Equation (1):

B+nH₂O+nCO₂→BH_(n) ^(n+) +nHCO₃ ⁻  (1)

Assuming all basic sites are protonated, the ionic strength, then,switches from zero to ½m(n²+n), as illustrated by Equation (2):

I=½m(+n)²+½mn(−1)²=½m(n ² +n)  (2)

where m is the molality of the additive.

TMDAB has two basic sites. Upon CO₂-treatment, ionic strength of aqueousTMDAB thus switches from zero to 3 m. For each of the CO₂ treated 1 mMTMDAB and 10 mM TMDAB solutions, a suspension was created with identicalpH and ionic strength as its TMDAB-treated counterpart. pH was adjustedwith HCl and NaOH. Ionic strength was adjusted with NaCl to reproducethe ionic strength imparted by 1 mM and 10 mM TMDAB (4 and 5respectively) or ammonium sulphate (hereafter AS) for the same set TMDABtreatments (6 and 7). Both 4 and 6 resulted in comparable settlingprofiles as a suspension treated with 1 mM TMDAB and CO₂ (FIG. 39).While corrected pH alone (3) was inadequate in promoting settling, 5 and7 were able to bring about similar settling profiles to a suspensiontreated with 10 mM TMDAB and CO₂ (FIG. 40). It is likely that settlingrates can be influenced by both pH and ionic strength. Higherconcentrations of TMDAB impart both increased pH and ionic strength;high pH impedes settling while high ionic strength does the opposite.This could explain the observed decrease in settling rate thataccompanied the increase in TMDAB concentration.

The supernatant turbidity measurements from pH and ionic strengthsettling tests further show that ionic strength is an important factorin reducing turbidity, as illustrated in FIG. 41.

Zeta potential measurements indicated that neither pH nor ionic strengthgave an adequate explanation of the behaviour brought about byCO₂-treated aqueous TMDAB on a microscopic level in terms of electricaldouble layer activities. Although the addition of electrolytesuccessfully decreased zeta potentials in comparison to the absence ofelectrolyte, increasing the concentrations of electrolyte (atcorresponding pH) did not produce the same trend as increasing TMDABconcentration (FIG. 41). However, an increase in particle size wasobserved at higher concentrations of electrolyte, which is consistentwith the trend in particle size with increasing TMDAB concentration(FIG. 42). pH alone was unable to produce the particle size trendimparted by TMDAB.

Corresponding Particle size pH Treatment z-avg (d · nm) PDI 4.90 Notreatment — — 4.25 CO₂ 980 0.202 4.75 1 mM TMDAB + CO₂ 939 0.305 5.95 10mM TMDAB + CO₂ 858 0.011

Corresponding Particle size pH I (mM) Treatment z-avg (d · nm) PDI 4.753 1 mM TMDAB + CO₂ 1092 0.247 5.95 30 10 mM TMDAB + CO₂ 1556 0.195

Thus, it appears that while pH and ionic strength are both importantfactors that affect clay suspension behavior, and ionic strength islikely the predominant mode of action through which TMDAB operates.

Example 33 Effect of Switchable Additives on Colloidal InteractionsFound in Oil Sands and Measured by Chemical Force Spectrometry

In this study, adhesion forces between bitumen and mineral surfaces weremodeled and studied by chemical force spectrometry (CFS), particularlyto demonstrate how switchable additives can be used to control theseinteractions, which are crucial to the bitumen liberation phase of theoil sands extraction process. Two organic functional groups commonlyfound in bitumen were selected to represent the bitumen: an aromaticphenyl group and a carboxylic acid group. Self assembled monolayers(SAM) terminated with these functional groups were formed on gold coatedAFM tips for CFS experiments. The mineral substrates investigatedinclude mica and silica, which are components of real oil sands systems(Takamura, K. Can. J. Chem. Eng. 1982, 60, 538. Gupta, V.; Miller, J. D.J. Coll. Inter. Sci. 2010, 344, 362-371). While clays such as kaoliniteand montmorillonite are, like mica, sheet-like aluminosilicates and arefound in oil sands, these minerals proved to be unusable in the chemicalforce experiments, due to extensive swelling in aqueous solution.Tip/sample interactions were analyzed as a function of pH, in thepresence of divalent cations (e.g. Ca²⁺, as used during the industrialprocess), and in the presence of switchable additives. As describedabove, CO₂ switchable chemistry is mediated by changes in solution pHdue to the dissolution of CO₂ and the formation of carbonic acid. Thus,further measurements to determine the effects of solution pH on theinteractions between SAM and mineral substrate, in the absence ofswitchable surfactant, were carried out. The literature related to oilsands chemistry indicates that divalent cations decrease bitumenrecovery through the promotion of adhesion between the bitumen and sandmoieties. The divalent cation both collapses the electrical double layerand shields the two negatively charged surfaces to increase adhesion(Iler, R. K. Chemistry of Silica-Solubility, Polymerization, Colloid andSurface Properties and Biochemistry; John Wiley & Sons, Hoboken U.S.A.,1979; and Maslova, M. V.; Gerasimova, L. G.; Forsling, W. Colloid J.2004, 66, 322). Calcium sulfate, a common additive to oil sandstailings, was used in the CFS studies to demonstrate how our modelsystems serve in mimicking real oil sands systems.

Experimental

Synthetic Methods

The synthesis of 12-phenyldodecanethiol was accomplished usingpreviously published literature methods (Lee, S.; Puck, A.; Graupe, M.;Colorado Jr., R.; Shon, Y. S.; Lee, T. R.; Perry, S. S. Langmuir 2001,17, 7364; Speziale, J. Org. Syn. Coll. 1963, 4, 396; and Frank, R.;Smith, P. J. Am. Chem. Soc. 1946, 68, 2103). The ¹H-NMR, ¹³C-NMR andmass spectra (high res, El⁺) matched those reported in the literature(Lee, S. 2001, supra). NMR and MS spectra showed that the product was amixture of the thiol and the corresponding disulfide (3:1 ratio by¹H-NMR) due to partial oxidation during the synthesis. However, it hasbeen demonstrated in the literature (Nuzzo, R.; Allara, D. J. Am. Chem.Soc. 1983, 105, 4481; and Bain, C.; Bieyuck, H.; Whitesides, G. Langmuir1989, 5, 723) that disulfides also self assemble onto gold surfacesthrough scission of the sulfur-sulfur bond. Therefore, this material canstill be used to create the desired self-assembled monolayers on gold.

N′-alkyl-N,N-dimethylacetamidines C4 and C8 were also synthesized bypreviously published literature methods (Liu, Y.; P. G. Jessop, M.Cunningham, C. Eckert, C. Liotta. Science 2006, 313, 958).12-Mercaptododecanoic acid was purchased from Sigma Aldrich and used asreceived.

Silicon (111) wafers were purchased from Virginia Semiconductors Inc.These substrates were cleaned and oxidized with piranha solution (3:1concentrated H₂SO₄: 35 wt % H₂O₂ in H₂O) for 1 hour prior to beingthoroughly rinsed with deionized water and dried under a stream ofN₂(g).

Muscovite mica (V-4 grade, SPI) was freshly cleaved prior to use. Doublesided tape was adhered to the surface and subsequently pulled off toreveal a new basal surface for AFM force measurements.

Instrumentation

AFM force-distance curves were obtained using a PicoSPM instrument(Molecular Imaging, Tempe, Ariz.) and a Nanoscope IIE controller(Digital Instruments, Santa Barbara, Calif.). All experiments wereconducted at 25° C.

Gold-coated silicon nitride AFM tips (CSC-38, MikroMasch USA; springcontant k=0.08 N/m; tip radius <10 nm, as per manufacturer'sspecifications) were functionalized for adhesion force measurements bysubmerging the tips in a 1×10⁻³ M solution of 12-phenyldodecanethiol(“phenyl tip”) or 12-mercaptododecanoic acid (“acid tip”) in isopropanolfor 24 h. Force measurements were conducted under aqueous conditions insolutions prepared using deionized water (18.2 MΩ, Millipore). Theadhesive force between the tip and the sample was determined frommeasuring the well depth of over 1000 force distance curves under eachexperimental condition. The adhesion force was measured approximately200 times at different surface sites. At least 5 surface sites weretested for each experimental condition, but typically 15-20 sites werestudied. At least 2 different tips were used in these measurements. Thelarge number of measurements was conducted to obtain a morerepresentative value of adhesion between the tip and the sample. Thereported values are an average of all the measured adhesive forces andthe errors are the calculated 95% confidence intervals.

The chemical force titration experiments were conducted using freshlyprepared unbuffered aqueous solutions of pH ranging from 3 to 11. Tomodify the pH, addition of 1.0 M NaOH solution was used to achievealkaline conditions and similarly a 1.0 M HCl solution was added toachieve acidic conditions. Unbuffered pH solutions were used to preventunwanted interactions between the surface and the ionic speciesassociated with the buffer. The pH values were checked before and afterthe experiment and the solutions were changed frequently to minimizechanges in pH due to the dissolution of atmospheric CO₂. Experimentswere carried out under low ionic strength conditions and the only ionsintroduced into the system were from the use of HCl and NaOH for pHadjustment.

For experiments involving CO₂ saturated solutions, the solutions werepretreated with CO₂ prior to acquiring the force curves. Ultra pure CO₂(Supercritical CO₂ Chromatographic Grade, Praxair) was bubbled throughthe solutions using a syringe for 30 min. For these force measurements,the AFM was outfitted with an environmental cell that was filled withCO₂ to maintain a CO₂ atmosphere around the aqueous solutions during theexperiment.

Results and Discussion

When switchable additives are activated or deactivated through theaddition or removal of CO₂ from the system, the solution pH is varied.Chemical force titration profiles (plots of tip/sample adhesion as afunction of pH) were measured for AFM tips functionalized using bothphenyl- and carboxylate-terminated SAM's with mica and silicasubstrates. These experiments were an important control case to monitorthe background effect of any solution pH changes. The chemical forcetitration profiles for the silica substrate and the acid and phenylterminated AFM tips are shown in FIG. 43A. Note that the forces measuredbetween silica substrate and the acid tip were scaled by a factor of 10relative to the remaining data in FIG. 43A.

The maximum adhesion force of 0.18±0.04 nN was measured at pH 4 in thechemical force titration profile between the acid tip and the silicasubstrate. The adhesion force dropped off rapidly at higher and lower pHvalues, which is similar to force titration profiles previously observedin systems where the tip and sample interactions are dominated byhydrogen bonding forces (van der Vegte, E. W.; Hadziioannou, G. J. Phys.Chem. B 1997, 101, 9563; and van der Vegte, E. W.; Hadziioannou, G.Langmuir 1997, 13, 4357). The surface pK_(a) of the acid-terminated SAMhas been previously observed to be at approximately 4-5, consistent withthe 4.9 pK_(a) of long-chain alkanoic acids in water. Assuming that thesilica substrate is negatively charged over much of the pH rangestudied, a large number of ionic H-bonds may form at or below thesurface pK_(a) of the tip, leading to the strong interactions observedin this pH range. At pH values above the pK_(a), the adhesion forcediminished sharply with increasing pH, as would be expected because thetip is becoming increasingly negatively charged and it is interactingwith a negatively charged substrate. Interestingly, the adhesion forceincreased again slightly at pH 11. This was a reproducible trend, seenin independent experiments. A possible explanation may be the increasein Na⁺ concentration from the increase in NaOH required to achieve thishigh pH. Both the silica substrate and the acid tip are expected to benegatively charged at pH 11 and the presence of Na⁺ cations may serve toscreen the two negatively charged surfaces. A maximum adhesion force of1.7±0.4 nN for the phenyl-terminated AFM tip and the silica substratewas observed at pH 7. The chemical force titration profile shows thatthe adhesion force decreased gradually at higher and lower pH values.This result is consistent with hydrophobic forces dominating thetip-sample interaction.

The chemical force titration profiles for the mica substrate and theacid- and phenyl-terminated AFM tips are shown in FIG. 43B. As with thesilica substrate, a maximum adhesion force (1.6±0.2 nN) between the acidtip and the mica substrate was observed at a pH of 4. This trend mayalso be attributed to hydrogen bonding interactions between thesubstrate and tip with a similar mechanism as outlined above. Adhesionforces between phenyl-terminated tip and mica substrate were weakthrough the entire pH range (FIG. 43B). Again, hydrophobic interactionsappear to be a main contributing factor in the tip-sample interaction.

In subsequent CFS experiments, the cationic switchable surfactant, C8(FIG. 44), was compared with C4, an amidine with a four carbon chaintail (FIG. 45). Unlike C8, C4 is not a surfactant molecule in thepresence of CO₂ due to its short alkyl chain length. However, both C4and C8 can be protonated in aqueous solutions saturated with CO₂ toyield a positively charged amidinium head group. Thus, comparison of C4and C8 determines to what extent changes in adhesion force may beattributed to the surfactant properties or simply due to the presence ofthe protonatable amidine functionality and consequent increase in ionicstrength following protonation.

The results from the CFS experiments in the presence of C4 are presentedbelow.

Adhesion Force (nN) Carboxylic Acid- terminated tip Phenyl-terminatedtip Additive Silica Mica Silica Mica 1 mM C4 0 0.01 ± 0.01 0 0.01 ± 0.01(pH 11 ± 0.2) 1 mM C4 + 0.18 ± 0.04 1.58 ± 0.18 0.07 ± 0.02 0.74 ± 0.35CO₂ (pH 5 ± 0.2) 1 mM C8 0.39 ± 0.20 0.23 ± 0.28 0.97 ± 0.33 1.97 ± 0.19(pH 11 ± 0.2) 1 mM C8 + 1.53 ± 0.19 1.94 ± 0.23 1.05 ± 0.38 0.41 ± 0.20CO₂ (pH 5 ± 0.2) pH 11 ± 0.2 0.10 ± 0.04 0 0.64 ± 0.09 0 NaOH ModifiedpH 5 ± 0.2 0.08 ± 0.05 0.31 ± 0.30 0.36 ± 0.26 0.35 ± 0.46 HCl Modified

A consistent trend was observed for all four tip/sample pairs. In theabsence of CO₂, there was no interaction measured between the tip andthe surface. Upon saturation of the aqueous solution with CO₂, theadhesion force increased dramatically.

Because the pH of solution changes due to addition of CO₂, the tablealso shows the adhesion forces observed in the absence of the switchableamidine, but at the same pH (using HCl or NaOH). For three of the fourtip/sample pairs, the increase in adhesion force that was observed inthe presence of C4 was greater than when the solution pH was modified byHCl or NaOH, and in one pair (carboxylate/mica) the increase wasdramatically greater. The observed modifications in adhesion forcecannot be attributed to pH changes alone.

The table also shows a similar set of data using C8, the activesurfactant species. The addition of CO₂ to the C8 solution caused adramatic rise in the attractive force for the carboxylate-terminatedtip, but not for the phenyl-terminated tip. Again, the changes inducedwere greater than what may be attributed to changes in pH alone. Unlikethe C4 case, the presence of C8 lead to significant adhesion forces forall four tip-sample pairs regardless of the presence or absence of CO₂.

The results from the CFS experiments suggest a mechanism by whichamidines such as C4 and C8 can reversibly control adhesion between thevarious components of an oil sand. They also show that such amidines maybe potentially useful as additives for the reversible manipulation ofthe water chemistry in oil sands extraction. In aqueous solutionscontaining these additives without CO₂, the adhesion forces between theorganic functionalized tips and the mineral surfaces were minimal. Thissuggests that this additive may be useful for decreasing adhesionbetween bitumen and mineral surfaces, thus facilitating bitumenliberation and flotation during the separation stage of oil sandsprocessing.

Gold-coated AFM tips functionalized with 12-mercaptododecanoic acid or12-phenyldodecanethiol were used as models of bitumen surfaces for astudy of adhesive interactions between these model bitumen surfaces andmica or silica. The parameters investigated included variations in pH,changes in calcium sulfate concentration, addition of amidine additivesC4 and C8, and the presence or absence of CO₂. In the chemical forcespectrometry experiments involving C4, the adhesion forces between theorganic functionalized AFM probes and the mineral substrates were low inthe absence of CO₂, but an increase in adhesive interaction was observedwhen in the presence of CO₂. The same trend was observed withexperiments involving C8, but only when the acid tip was used. The lackof a CO₂-triggered increase for the phenyl tip may be due to thehydrophobic tail of C8 being attracted towards the phenyl tip.

Of the two switchable additives studied, C4 was most consistent inswitching on and off the adhesion interactions between all of theorganic and mineral pairs, while C8 only showed that effect with thecarboxylic acid tip. This suggests that C4 can be useful forfacilitating bitumen and mineral separation in the extraction phase ofthe industrial process.

Example 34 Titanium Oxide Settling with Switchable Water Additives

This titanium oxide settling study was used as a model for waste watertreatment to remove unwanted particulates using a switchable additive.

The titanium(IV) oxide (nanopowder, ˜21 nm particle size, X9.5% tracemetals basis) used was purchased from Sigma-Aldrich.

In this study 0.050 g of 3-(dimethylamino)-1-propylamine functionalizedPMMA (MW=120,000) was placed into two different 250 mL round bottomflasks equipped with a 2 cm Teflon stir-bar. 100 mL deionized water wasadded and the solutions were stirred (600 rpm) until the polymerdissolved (10 min to 16 h). Then 1 g of titanium(IV) oxide was added.Both suspensions were stirred at 600 rpm for 1 h, while CO₂ was bubbledthrough one of the solutions using a gas dispersion tube. After that,both suspensions were transferred into 100 mL graduated cylinders andthe settling rate was monitored over time. In the presence of CO₂ veryquick bulk settling was observed in the presence of CO₂, leaving aturbid supernatant behind that cleared up within 2 h. Without CO₂present no settling was observed, resulting in a stable suspension. Thesupernatant in the presence of CO₂ was only slightly turbid, whereaswithout CO₂ the supernatant consisted of a stable suspension that wasnot transparent at all. These results support the use of the switchableadditive in a waste water treatment process.

All publications, patents and patent applications mentioned in thisSpecification are indicative of the level of skill of those skilled inthe art to which this invention pertains and are herein incorporated byreference to the same extent as if each individual publication, patent,or patent applications was specifically and individually indicated to beincorporated by reference.

It will be understood by those skilled in the art that this descriptionis made with reference to the preferred embodiments and that it ispossible to make other embodiments employing the principles of theinvention which fall within its spirit and scope as defined by theclaims appended hereto. All such modifications as would be obvious toone skilled in the art are intended to be included within the scope ofthe following claims.

1-126. (canceled)
 127. A system for modulating ionic strength of anaqueous solution comprising: a switchable water comprising water and anadditive switchable between a first form and a second form, wherein saidsecond form of the additive includes at least one ionized functionalgroup that is neutral in said first form of the additive, such thatswitching the additive from the first form to the second form increasesthe ionic strength of the switchable water; and means for contacting theswitchable water with an ionizing trigger to ionize at least onefunctional group in the additive and thereby increase the ionic strengthof the switchable water; wherein the additive is a polymer.
 128. Thesystem of claim 127 for modulating an osmotic gradient across amembrane, said system additionally comprising: a semi-permeablemembrane; and means for contacting the semi-permeable membrane with afeed stream on the other side of said semi-permeable membrane
 129. Thesystem of claim 128 for use in removal of undesirable solutes orparticles from water.
 130. The system of claim 129 wherein the system isa desalination system, such as for treatment of seawater or brackishwater, or a wastewater remediation system.
 131. The system of claim 128for use in concentrating a dilute aqueous solution.
 132. The system ofclaim 131, wherein the dilute aqueous solution is wastewater.
 133. Thesystem of claim 127, wherein the system additionally comprises means forcontacting the switchable water with a non-ionizing trigger toneutralize the at least one functional group ionized by the ionizingtrigger and thereby switch the additive from the second form to thefirst form.
 134. The system of claim 133, wherein the non-ionizingtrigger is (i) heat, (ii) a flushing gas, (iii) a vacuum or partialvacuum, (iv) agitation, (v) a strong base, or (vi) any combinationthereof.
 135. The system of claim 128, wherein the system additionallycomprises means for contacting the switchable water with a non-ionizingtrigger to neutralize the at least one functional group ionized by theionizing trigger and thereby switch the additive from the second form tothe first form.
 136. The system of claim 135, wherein the non-ionizingtrigger is (i) heat, (ii) a flushing gas, (iii) a vacuum or partialvacuum, (iv) agitation, (v) a strong base, or (vi) any combinationthereof.
 137. The system of claim 127, wherein the polymer has at leastone nitrogen-containing functional group that is sufficiently basic tobe protonated when the polymer is in the presence of an ionizing trigger138. The system of claim 137, wherein the at least one nitrogen beingsufficiently basic to be protonated by the ionizing trigger has aconjugate acid with a pK_(a) in a range from about 6 to about
 14. 139.The system of claim 138, wherein the pK_(a) is in a range from about 8to about
 10. 140. The system of claim 137, wherein the ionizing triggeris a Brønsted acid, or a gas that when dissolved in water reacts withwater to liberate hydrogen ions.
 141. The system of claim 140, whereinthe Brønsted acid is hydrochloric acid, formic acid, sulfuric acid orcarbonic acid.
 142. The system of claim 137, wherein the ionizingtrigger is CO₂, NO₂, SO₂, SO₃, CS₂, or COS.
 143. The system of claim127, wherein the polymer is insoluble in water when in the first form.144. The system of claim 127, wherein the polymer is at least partiallysoluble in water when in the first form.
 145. The system of claim 127,wherein the polymer is: a biopolymer or a derivative thereof; afunctionalized branched or linear polyethyleneimine, such as amethylated polyethyleneimine (“MPEI”), an ethylated polyethyleneimine(“EPEI”), a propylated polyethyleneimine (“PPEI”), or a butylatedpolyethyleneimine (“BPEI”); a functionalized polymethyl methacrylate(“PMMA”) based polymer, such as 3-(dimethylamino)-1-propylaminefunctionalized PMMA; a functionalized polyacrylic acid (“PAA”) polymer,such as 3-(dimethylamino)-1-propylamine functionalized PAA; anamine-containing polyacrylic acid salt; a functionalized poly(methylmethacrylate-co-styrene) (“PMMA/PS”), such as a3-(dimethylamino)-1-propylamine functionalized PMMA/PS; a polymersynthesized from amine-containing monomers, such as apolydiethylaminoethylmethacrylate (“PDEAEMA”); or any combinationthereof.
 146. The system of claim 127, wherein the system additionallycomprises means for separating the additive from the water in saidswitchable water.
 147. The system of claim 146, wherein the means forseparating the additive from the water comprises a reverse osmosissystem.
 148. The system of claim 146, wherein the first form of theswitchable additive is immiscible in water and the system additionallycomprises means for decanting the first form of the additive from thewater.
 149. The system of claim 146, wherein the first form of theswitchable additive is insoluble in water and the system additionallycomprises means for removing the insoluble first form of the additive,such as by centrifugation, filtering, skimming or nanofiltration.
 150. Amethod for modulating the ionic strength of an aqueous solution,comprising: (a) contacting a switchable water comprising water and anadditive switchable between a first form and a second form, wherein saidsecond form of the additive includes at least one ionized functionalgroup that is neutral in said first form of the additive, such thatswitching the additive from the first form to the second form increasesthe ionic strength of the switchable water, with an ionizing trigger toionize at least one functional group in the additive and therebyincrease the ionic strength of the switchable water; wherein theadditive is a polymer.
 151. The method of claim 150, for removing asolute from the aqueous solution or for concentrating the aqueoussolution, wherein the method additionally comprises the steps of: (b)providing a semi-permeable membrane that is selectively permeable forwater and has on one side a draw solution that comprises said switchablewater, wherein the step of contacting the switchable water with theionizing trigger to switch the additive to the second form is performedbefore or after association of the switchable water with thesemi-permeable membrane to increase the osmotic pressure of the drawsolution; (c) contacting the semi-permeable membrane with a feed streamof the aqueous solution to permit water to flow from the aqueoussolution through the semi-permeable membrane into the increased ionicstrength draw solution; and (d) optionally, removing the additive fromthe resulting diluted draw solution.
 152. The method of claim 151,wherein the solute is a salt.
 153. The method of claim 152, wherein thefeed stream is an aqueous salt solution, such as brackish water or seawater.
 154. The method of claim 151, wherein the feed stream is wastewater.
 155. The method of claim 151, wherein step (d) comprisescontacting the diluted draw solution with a non-ionizing trigger toswitch the additive to its first form.
 156. The method of claim 151,wherein step (d) comprises a reverse osmosis.
 157. The method of claim155, wherein the first form of the switchable additive is immiscible inwater and step (d) additionally comprises decanting the first form ofthe additive from the water.
 158. The method of claim 155, wherein thefirst form of the switchable additive is insoluble in water and step (d)additionally comprises removing the insoluble first form of the additivefrom the water, such as by centrifugation, filtration or nanofiltration.159. The method of claim 150, wherein the polymer has at least onenitrogen-containing functional group that is sufficiently basic to beprotonated when the polymer is in the presence of the ionizing trigger.160. The method of claim 159, wherein the ionizing trigger is a Brønstedacid, or a gas that when dissolved in water reacts with water toliberate hydrogen ions.
 161. The method of claim 159, wherein theionizing trigger is CO₂, NO₂, SO₂, SO₃, CS₂, or COS.
 162. The method ofclaim 160, wherein the Brønsted acid is hydrochloric acid, formic acid,sulfuric acid or carbonic acid.
 163. The method of claim 159, whereinthe at least one nitrogen being sufficiently basic to be protonated bythe ionizing trigger has a conjugate acid with a pK_(a) in a range fromabout 6 to about
 14. 164. The method of claim 163, wherein the pK_(a) isin a range from about 8 to about
 10. 165. The method of claim 150,wherein the polymer is: a biopolymer or a derivative thereof; afunctionalized branched or linear polyethyleneimine, such as amethylated polyethyleneimine (“MPEI”), an ethylated polyethyleneimine(“EPEI”), a propylated polyethyleneimine (“PPEI”), or a butylatedpolyethyleneimine (“BPEI”); a functionalized polymethyl methacrylate(“PMMA”) based polymer, such as 3-(dimethylamino)-1-propylaminefunctionalized PMMA; a functionalized polyacrylic acid (“PAA”) polymer,such as 3-(dimethylamino)-1-propylamine functionalized PAA; anamine-containing polyacrylic acid salt; a functionalized poly(methylmethacrylate-co-styrene) (“PMMA/PS”), such as a3-(dimethylamino)-1-propylamine functionalized PMMA/PS; a polymersynthesized from amine-containing monomers, such as apolydiethylaminoethylmethacrylate (“PDEAEMA”); or any combinationthereof.
 166. The method of claim 150, wherein the polymer is insolublein water when in the first form.
 167. The method of claim 150, whereinthe polymer is at least partially soluble in water when in the firstform.
 168. The method of claim 150, additionally comprising the step ofcontacting the switchable water with a non-ionizing trigger toneutralize the at least one functional group ionized by the ionizingtrigger and thereby switch the additive from the second form to thefirst form.
 169. The method of claim 168, wherein the non-ionizingtrigger is (i) heat, (ii) a flushing gas, (iii) a vacuum or partialvacuum, (iv) agitation, (v) a strong base, or (vi) any combinationthereof.